Best way to prepare to paint over high gloss paint?
I'm painting an acrylic front door a very deep red. I've primed and then applied the first coat. I've read that I need to lightly scuff it before the second coat. On the parts shown in the photo, I'm not sure if sandpaper should be used because it has the ins and outs that will be hard to do. OR, I read that using TSP instead of sandpaper works fine or also a de-glosser instead of sanding. What would be best? Would TSP or a de-glosser be harmful?
ALSO, a while back I painted a small bathroom a lightish brown in high gloss but now want to paint it again in a lighter color and a satin finish. So, the same questions apply to it.