I wanted to paint and weather the wheels as well. The only way to get at the wheel sides is to disassemble the complete truck. So that is what I did. In the picture below you can see all the parts. Before proceeding I took the opportunity to wash the parts in alcohol. I also masked the wheel threads and stuck the bearing caps to the ends of some tooth picks for easier handling.
I spray painted the wheels with Tamiya red brown, followed by a dusting of AIM light rust weathering powder.
The truck parts were sprayed with Vallejo black surface primer. The truck was then reassembled. The painted and weathered wheels were also fitted again. I then hit some parts of the truck, such as the visible part of the bolster and the springs, with some acrylic raw umber. Last the trucks were dusted with AIM dark rust, medium earth and medium gray powder. The dark rust was applied around the same areas that got the sienna, the medium earth mainly along the lower part of the truck, and the medium gray all over the truck.
The picture below shows the finished truck to the right, and for comparison an original Atlas truck (with P48 profile) wheels to the left.