Which site or forum that these centralized mixers will promote their projects? 
Or these mixers will don't have any medias to promote except volunteering by themselves? maybe hire someone who willing to shills/spams?
There are other blog and media platforms, Review sites, other forums etcOr these mixers will don't have any medias to promote except volunteering by themselves? maybe hire someone who willing to shills/spams?
Bitcointalk signature advertising was quite unique for them, but there are other places the mixers can advertise from. If you want to prove this, just Google up one of those old mixers that was not advertising in the forum like cryptomixer