U can get universal wax that is kinda like prep wax for your base. its better to use this because if not, ull have to buy wax for different temperatures which becomes expensive and annoying.
Dont use rub on.. its used for racers. they rub it on right before their race and it last about 1 or 2 runs.
My opinion, when base starts looking white ish, put universal wax on with an iron, once its dry, scrap it off with a plastic scrapper, and if u really want to do a good job, purchase a rough and a soft brush (Swix make a nice rough brush (white) and soft brush (blue).) After scrapping, pass the white brush, then the blue one. this will really give your skis a nice finish.