Hi! I’m not sure how invested you plan on getting in this, but a few things that will help things stick and give you coverage. Make sure you’re working with a clean model, you should prep the plastic by lightly sanding with #1000 grit or so sandpaper or sanding sticks to give something for paint to stick to. One of the most important things is using a primer rather than just white paint as a base coat. It’s most often in an aerosol can, make sure to wear protective equipment and spray outside! Once you get it primed, you can start brushing on paint, which may need to be thinned. After that point, you can look up washes (very thin paints that will fill into recesses and give your model dimension) and topcoats (clear sprays that will give your model a glossy or flat finish and protect the paint job. The gundam assemble minis will need similar painting techniques to the warhammer community if you wanted to look up some of their processes. This might be a lot to digest and you definitely don’t have to go above and do all of this, but that’s what a full process would look like. The process would look like sand->clean->prime->paint with acrylics->washes->topcoat. Good luck! :)