I was chatting with a guy on Grindr too last week. He is a sub and wanted to be tied up. I said I'd do it if he was ok with me giving him a good pieing. I was quite business like about it all.
I just asked him if he was into wam- he said he hadn't heard of it so I sent him a link. He seemed pretty keen and didn't run off!
Once told a guy the only way I'd suck his dick is if he covered me in marshmallow fluff and Chocolate. Ended up sucking his dick while chocolate rained down my sticky face. You can for sure get guys into wam off Grindr