I'm restoting a Joust and have used a spray gun for the sides, spray can for the front, and roller for the top and back. I have very little painting skill, but did spend some time reading and lots of time preping...
I highly recommend the spray gun. Even my cheapie $100 HVLP home sprayer did a good job with proper preparation (see
http://www.tutankham.com/painting.htm). Much better than rolling or brushing - even for the unskilled.
For the front, back and harder to get areas on an assemble cab, I was happy with the spray can. The roller was need for area that were too difficult to get with the sprayer and, despite sanding, priming, etc, still needed a direct application.
Since your cab is being built and in pieces to start with, I think spraying will come out great. If you do have to thin your paint, save the extra or note the thinning ratio for any touch up needs after assembly and movinng.
Good luck!
John VV