1 base cleaner is the snake oil of the ski world, it does nothing but dry the bases out, its a solvent designed to break down wax not remove dirt. It will stay in the micro pores of the base and reduce the adhesion of subsequent waxing. Hot scraping to clean the bases is far more effective as it lifts out the dirt, hot scrape then bush out with a steel brush is the best way.
2 Never and I mean never run an iron over a bare base, if you slipped or the temp was wrong then your going to melt your base.
3 Your much better off crayoning wax on the bases then dripping a litte on top of that, it reduces the chances of hot spotting and means the iron will never touch bare base.
Some bases (usually VHGC race bases) do not retain wax for that long. The bases on my pow skis will hold wax far longer than my GS skis.