The Tamiya polishing compound will work great. Clean the window well with warm water and soap to get rid of all trace of polishing compound residue. After the paint has been applied and cured, apply some Tamiya wax to the glass. It really makes the glass come alive, but no painting can take place after the wax has been applied. The same goes for glue on waxed surfaces.
When using the polishing compounds, be careful to not stress the glass. I find that as I am polishing, my slippery, polish covered fingers tend to grip the glass tightly which can cause it to flex and induce micro stress cracks.