AUTO (Vanguard/Rearguard circle): Once per turn: Generation break 1: (Active if you have 1 or more face-up G Units in your vanguard circle or generation zone) [Counterblast 1] When this unit attacks a vanguard, you may pay the cost. If you do, choose another of your rearguards, stand it, until end of turn it gets Power +4000, during the end phase of this turn, retire that unit. (Even if you do not pay the cost, this ability cannot be used for the rest of that turn.)
ACT (Vanguard circle): Once per turn:
[Counterblast 1 and choose a face down card named “Omniscience Dragon, Managarmr”
generation zone, turn it face up] If the number of face up cards in your
generation zone is two or more, choose up to two of your rearguards, until end of turn they get Power +4000 and "AUTO (Rearguard circle): When this unit attacks a vanguard, if this unit's Power is 20000 or more, until the end of that battle your opponent cannot call grade 1 or greater cards from their hand to the guardian circle."
Managarmr's unique skill turns any 16000 power rearguard lane into a 20000 power one, automatically meeting the conditions for the skill he endows those rearguards with. The benefit of having rearguards that cannot be blocked with perfect defense cards is innate, but Tusk Master brings something else to the table; not only will he make a 22000 power column with a base 7000 booster, Tusk Master's counterblast will allow a frontrow rearguard that has received Managarmr's skill to attack a second time with that same skill still active. The trouble with this is meeting the minimum 20000 power requirement on both attacks. Most units will only reach 17~19000 power on this second attack, but there are ways to circumvent this. The grade 2 generation break attacker Malicious Sabre is one, as he automatically attacks for 12000 power as long as there is at least one face-up G unit in play, so with both Managarmr and Tusk Master's power bonuses his second attack will reach the 20000 power threshold unboosted. The first vanguard options Pencil Koala and Telescope Rabbit can also cause a similar result on a less innately powerful unit and cause its final power to break the 21000 threshold unboosted, but Koala has to boost a vanguard attack that hits at a late stage in the fight while running Rabbit involves giving up her boost for that turn and devoting another counterblast to the strategy. On a more practical level, as long as you ride him successfully Big Belly's own on-stride counterblast will give two rearguards +4000 power, causing a boosted Tusk Master to reach 26000 power and the other rearguard to break the 21000 line innately.
Resist to prevent him from being targeted by retire or lock skills. The key to manipulating Tiger is that his skill is once-per-turn and cannot be used again if it is not used when the conditions are met, but if you attack with him unboosted then you have not fulfilled the timing for his conditions. This means that if you stand Crayon with Tusk Master and attack with him again but boosted, you will be meeting the conditions for his once-per-turn ability for the first time that turn.
5/21/2015 Update: A ruling made in mid May on Magnum Assault stated that the timing for Crayon's type of generation break units is "when it attacks a vanguard" and that being boosted is not a part of his timing. This means that the only way to use Tiger like this is to attack a rearguard. The text below this point has been modified to accommodate this ruling.
Therefore, you can power up Crayon Tiger with Managarmr, attack with a rearguard for 13000 power, attack with Tusk Master to stand Crayon and give him +4000 power, then attack with Crayon boosted and use his counterblast 1 to give his booster +4000 power. (Note that because boost is applied continuously until a unit changes circles, standing the unit will not cause it to stop boosting even if stood--compare Dancing Wolf.) While the check timing for skills that activate "when this unit attacks" takes place after boosting, because the power from a boost is added continuously (see Comprehensive Rules 18.104.22.168), the power bonus given to Tiger's booster will be applied to him, causing him to reach a total of 28000 power while also blocking grade 1 and greater cards from being called from the hand.
The initial 13000 power attack drains 5000 additional shield from either the opponent's hand or intercept-cabable cicle, Tusk Master drains 15000~20000 (draw triggers are becoming less common and therefore a 21000+ power column that can only be blocked by grade 0s tends to take an additional 10000 shield rather than 5000) Managarmr takes the opponents' perfect defense card and the card they discard for it, and Crayon takes a guaranteed 20000 to block or otherwise forces the opponent to take damage. A turn like this takes a good seven card hand to defend, in total 40~45000 shield and one perfect defense for the center lane. Moreover, Tusk Master can be better abused with Sleeping Tapir, who will ultimately cause a -1 in card advantage but has better chances of ending the game on that turn. Since unlike Tiger, Tapir is not once-per-turn and so will have two opportunities to power up his booster using the same pattern described above, his final attack will climb up by an additional +4000 power--up to 32000.
Tusk Master is not an independent killing machine, but is an important support card that can make critical plays in conjunction with the rest of Great Nature's combo deck. There are a myriad number of ways to use him effectively, but some trains of thought will invariably lead in circles. Ultimately he is best used as in the Han Feizei's paradox; as an unstoppable spear.