The little metal track from the factory that supported the curtains via small plastic balls that fit in the track is excellent, but I could not find any of the track, and most of mine was missing.
My curtains were folded over and sewn at the top and bottom so that a dowel could be inserted, and the dowels were set over little brass hooks screwed into the wooden trim. I don't recommend this, the dowels warp and if someone grabs a curtain and pulls, the dowel breaks.
I used 5/16" shock cord (black looks good) instead of the dowels, stretched tight above the windows. This stays straight, looks good, and if someone tugs on it, it will snap back again.
For the windshields, I use reflectix fastened with velcro, because a lot of heat will come in there, especially in Florida.
1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida