Can I use Sandtex undercoat primer to my fiberglass garage door and a exterior gloss finish afterwards?

I often see pictures of rooms painted with different colors on different walls. I would like to use a dark, rich red color in a basement room but only want one or two walls this color. I would think all the walls this color would make it too dark or

I just painted some very old wooden cabinet doors a dark brown color. I just discovered the “Smooshing” technique and I wonder, can I use a lighter color to smoosh over that dark brown? Thank you!

I tried to clean spots off of my wall and now the spots are worse. Can I fix them without repainting the whole wall?

A contractor sprayed the outside of my house and now it has spots that have bubbled up and peeling along the boards has also taken place. Is this due to not preparing the surface first?

I painted my bedroom and realized after that on the ceiling I still have a couple spots that we spackled but not sanded down and also small dried drips of paint on the walls. Can I still sand and then paint over? What is the best thing to do? Appreciate

We are getting ready to paint an old bathroom. The paint has alligatored. What preparation is necessary? I believe the old paint is enamel. Do we need to sand down the old paint?

My fiberglass entry door and side lights were gel stained 5 yrs ago. The stain has faded and some peeled off. (Maybe partly due to facing the west sun and weather). I would like to redo the door, but this time with paint. I need to know how to do

We are remodeling upstairs in our home and I am trying to find the right color for my daughter’s new bedroom. There is light pine wood on the ceiling which slants down on two sides and medium stained baseboards and trim around one big window that faces north. The room