I just thought I would share a technique I've been using to paint the wheels on my 1/48 scale aircraft and that's been working for me quite well lately. I'm sure other people probably have been doing this themselves but it just happened to discover it myself.
It involves using circle stencils like the one in the link below:
https://www.amazon.com/Staedtler-Combo-Circle-Template-977/dp/B000KIBQ46
I purchased mine from Michaels for about $5
Painting wheels:
Since the circle sinces are pretty standard, as are the wheel hub sizes. I normally start off by painting the entire wheel (hubs and tires) black or whatever color rubber you're planning on using. After the base layer is dry I pick up the wheel on one hand and try to find the circle shape on the stencil the best matches the hub diameter of the wheel. After finding the correct size I normally hold the stencil over the wheel in one hand and quickly airbrush the hub with the other.
This technique has given me perfect results every time and looks the cleanest to me out of everything else I have done. What I like about it, is it is really quick to do and requires no prep work with tape or putty masking etc...