What you want to do is called "fairing," it means making smooth by filling in the valleys. It doesn't have to be epoxy
. It can be Bondo, as used in auto body work. It can be epoxy with a filler that makes it easy to spread smoothly and sand to a fine smooth finish. You probably don't even really have to sand the existing paint
, as long as it is in good condition and clean so your fairing can adhere. There are instructive videos and literature available. One source of information is the Gougeon Brothers' WEST System website.