3. Preparing for paint

Using sandpaper you can remove any marks from the supports, as well as make the surface as smooth as you want. Using wet sandpaper will also save you from some dust. For some extra pro tips for sanding 3D prints, click here.

Next, if your design is comprised of different pieces to be glued together, you can use a silicon glue gun and tie together/hold still the glued parts until the silicon cools off.

As a last step before the paint, you can spray your design with a primer filler.
Primer filler is a type of primer that fills small surface imperfections. Use a piece of cord to tie around your design and hang it in an open space with good ventilation (open the windows!).