No shine after rain

If your paint is old, I would consider doing the Mothers 3-stage set up (Stripper/cleaner, polish, carnuba wax) just to make sure you're getting the best shine out of your paint. If your paint is really oxidized, I would also recommend going over it with a clay bar to clean it up some.

That being said, how are you washing it between wax jobs? Some soap’s contain a lot of detergent in order to strip road grime, but the unfortunate draw back to this is, that it strips the way finish as well. I would recommend a low detergent soap as a replacement for whatever you're using now.

Also, stay away from car washes. The coarse brushes and soaps will buff the finish right out of your paint. This goes for the touch less washes too. They just replace the brushes with even more powerful soap.

Finally, if you want to be really meticulous about it, I would rinse and chamois your car and the wheels after it rains. This will ensure there are no water spots and that particulates in the air don't adhere to the finish.