I would not bother with that paint. You are going to be dealing with a very messy product there and a hell of a lot of effort getting in on to the walls. Plus it will take days if not weeks for the smell do dissipate. It is a lot of effort when plain white paint will be nearly as good. Better yet, go to home depot and get some Reflectix. It is highly reflective and you can hang it in 1/2 hour and your are done.

The benefits of repotting far outweigh any stress to the plants. You put them in a big pot and the roots are going to stretch and stretch as they never meet any resistance. You want dense root development to support a dense canopy. You will have significantly better results starting in a small pot, moving up to 1 gallon and then into the 5 gallon pot.