Essentially it’s like using resin in place of a body filler like Bondo, with the advantage here being that the resin cures in seconds. The thick resin fills in tough spots quickly. Now to be ...

Other UV resins should work similarly from what I understand, but I haven’t tested them. Sanding, usually along with using fillers like Bondo Smoothing with solvents (e.g. acetone vapor bath for ...