I have a 26ft TT which is painted white, still turns into a sweltering hot box in the deep south with 90F+ temps.
Don't bother slathering white paint on your rig unless the existing paint is worn out, just not going to notice the difference and will cost you more in paint that it is worth.
RVs just simply do not have enough insulation (R3 or a bit less), they have dark single pane windows which also does not help the cause one bit.
Best you can hope for is a few trees to park it under for some shade, you would be surprised at the cooling effect trees have on objects located under them..
