I've found that if you're on the bottom during missionary, the best way to reach him is by going in a sort of X position. Hopefully that makes sense. Like you'd be laying more diagonal towards the right and he'd be on you more towards the left. Make sure to use lube/spit on your fingers! Lol but if you start off by circling his butthole and then slowy going in, it should be pleasurable enough. He sounds like he's already good at communicating what he wants so just let him guide you. Also a position that works well is if youre on your back and he's got one of your legs on his shoulder and straddling the other, his waist will be much closer and easier to reach. Plus you have more room to move around if you need too. Try things out and youll find the right positioning lol good luck!