I found the easiest way to remove the paint chalk is to just wash the siding with regular soap, with a few oz of bleach, in 5G water, and a can of cheap scouring powder. I sprinkled scouring powder on the wet sponge and washed lightly so as not to create swirls in the paint from the cleaning action of the powder. When the RV is dry, follow up with a cleaning wax. That was my method when we had an aluminum-skined 5er.
2000 Winnebago Ultimate Freedom USQ40JD
, ISC 8.3 Cummins 350, Spartan MM Chassis. USA 1SG, retired;PPA,Good Sam Life member."We the people are the rightful masters of both the Congress and the Courts - not to overthrow the Constitution but to overthrow men who pervert theConstitution. "Abraham Lincoln"