I have been a aircraft mechanic for years and have stripped quite a few light aircraft for painting. If you are going to strip the old paint off use a liquid stripper never sand it. Never use a steel or brass brush or steel wool on aluminum. Micro particles of the steel can break off and get embedded in the aluminum and set up dissembler metal corrosion and you will have a hole in time. Never mark aluminum with a lead pencil and leave the mark as the same can happen. We would strip the aluminum then wash the stripper and old paint off then wipe the entire skin down with methyl ethyl ketone (MEK). If a area needed extra scrubbing we did that with a non metallic scotch brite type pad with the stripper or MEK. The skin is then ready to paint.If you are going to paint over the old paint, which I think most would, remove all old silicone type sealants then wipe down the entire area to be painted with MEK to remove old wax. The MEK works much better than paint thinner. Buff the old paint lightly with aluminum sand paper or silica paper so the new paint sticks better. Some of the best paints I have used is Dupont Imron and Alumigrip. Many auto paint stores carry these. They are not cheap but most of the expense and time go into preparing the surface so use the best paint if you can afford it, and you plan to keep the HI-LO for years. If you decide to do this yourself follow the paint manufactures recommendation for prep as there are many different paint systems available. I never did the painting myself as we wanted the A/C to look great, not like a jackleg did it. I have painted my kids cars before but they paid me nothing so couldn't complain. Hope some of this helps.