Yesterday I spent no small amount of time cleaning the shop of all the dust resulting from the last week's sanding. Today I placed micro on the upper surface of the left aileron, to prep for primer. There is really not a lot to fill on this surface, no more than 1/16 or an inch, but that's still not dead flat. So having learned from experience, I laid a lot of micro down, so that I'll have to fill only once. Removing excess micro is not hard over this relatively small surface, so why not?