i have a very large belly, and a really big fupa. my fupa flesh covers my penis completely, even when erect. to handle it, i need to lie on my side, which gets the belly out of the way, and then press my hand down to squish the fupa flab out of the way. so, it's not really a comfortable thing to do (oddly, it is hard on my shoulder).
i have heard from other guys here in a similar situation that they could masturbate just by manipulating their fupa.
unfortunately that has not worked for me.
there are lots of toys out there to help, though.
and having a partner who gets turned on by all of this helps, too!