Start complaining about grindr and see if he agrees.
Look through his phone when he's not looking.
Grab his balls.
Throw out stuff like "(athlete) is hot, don't ya think?" If they say "Nah ***** are you gay?", then just say "I meant like 'on fire,' not hot you gay face.
Leave them alone and let them reveal when they are ready too.
but i just want to encourage him that being true and honest to yourself is the best way in order for him to accept himself because i can really see that he is insecure and stuff like that
Send a dick pic and don't acknowledge it until he responds. When he does, he'll either send one back, or he'll say "wtf man?!", in which case you say you sent it to him by accident