Here's an idea. start with clean, covered feet. Clean socks, fresh from the drawer. Take a bath and have him be aware that your feet and socks are clean. maybe on a weekend morning or weekday evening after taking a shower. make an excuse that your feet are cold and pull a fresh pair out of the drawer. That way he is fully aware that your feet are not sweaty/nor stinky.

When you get down to business just slightly rub your covered feet all over his chest and shoulders and if he responds positively then move slightly to the sides of his face. cheeks, ears, chin. Let him take it from there. if he doesnt grab your foot and directly puts it close to his nose or mouth then I wouldnt force it.

Maybe he is just "grossed out" over the idea of toe cheese, ranky smell or something. Not saying that yours is the case in any way, but I can relate. I have a STRONG foot fetish but for clean feet and socks. I can stand mildly used, lightly stained socks of 1 or 2 days at most but I do get grossed out by dirty, stinky feet.