My father in law paints just about anything (he's definitely not into bikes though) and always with a paint brush!
My husband painted a whole Troopy with a paint brush once, it was a hammered metal finish so not that hard to come up looking pretty ok.
Me I like the spray can, particularly for bigger stuff (like a kids table, mail box etc), I'm just crap at painting with a brush and have no real patience or desire to persevere & do a better job.
So if you don't mind masking it all off (could be easier if you take your tires off?) and you don't mind going through a few cans of paint then spray it. I think it's easier to get a good finish this way.
Or alternately if you don't want to spend a huge amount of time masking or go through a heap of paint, and you think you have the patience & care then do it with a brush. I suppose the right type of brush & technique would leave no brush marks, but then again how noticeable would they be on spokes anyway! I can see the other benefit is that you can alternate colours too which would be a lot harder to do using a can!