Let's be my usual blunt self: You have a place to play, and equipment to sell, that is designed 100% for paintballers. Why not stick to that clientele?
You said you had played airsoft before, and others agreed. You should know the problems a paint grenade can cause to an airsoft gun by now. So either adapt your products or stop trying to get one clientele to buy products meant for another clientele.
If you want to do buy/sell, there is a section of the forums for that. If you are serious, you will also get age-verified so you can do transactions here.