As mentioned sanding resined fleece is a pain. Get some tshirt material at a local fabric store, use that for your shape. One, it takes far far less resin to soak it (fleece absorbs like crazy). Two it tends to stretch easier than fleece. Three, it will be smooth unlike fleece which will be fuzzy. Once you have the shape, then use fiberglass on inside for strength.
That way you have the strength from actual fiberglass and the smooth outside from the thinner fabric will take far less sanding and far less filler to finish off.