The trick could be to establish yourself with minimum credibility not make it seem like your promoting it, with just the right touch I would imagine.
Might involve chatting up the groups a bit as prep. Then seeing if you can get a discussion going in relavant context. You could be on the fence about it or grudgingly aginst the product with a ringer, who could also be you, whatever.
Seem unprofitable time wise though, I would just try being a sort of established member on an on and off again basis of groups that interest you anyway, and sharing what works in a subtle way or offering as a solution to question asked by another member.
Another tactic that might be able to be used is, vpn, multiple accounts creation/software and spamming like mmo gold sellers, after each ban, prob most effective method.
These sellers on mmos though have learned to create better classified ad copy though lately and toned it down so there is less of a hate and more of an interest response though.
The friendly nonevasive tactic probably works better than the obnoxious push as far as spamming. They even use cute little emotes. lol
Just a few thoughts.