Stage is an easy question -- you cannot paint first and then print as you cannot print exactly in the same position,  thus you print the decal first and then paint.  Not knowing the effect of the paint on the print, you would probably want to protect the printing with a couple of thin layers of clearcoat lacquer first.

Since you are working on the decal rather than the bike, you can have it flat so you can used thinner paint without running -- and multiple thin coats of thin paint will not show brushstrokes.

As I have not actually done any of this it is pure speculation.  On the other hand, you will be doing on the decal rather than the bike so you can do several decals until you get one that is good enough (it will never be perfect.)

If you want more than what you can get from a decal you can afford airbrush custom art if you could find someone like my 16-year-old daughter.  Fantastic artist who is her own worst critic.  She does not have an airbrush and could likely be talked into doing the artwork in exchange for an airbrush set (which is not that expensive.)  To paint a tank or fender -- replace with a spare and hand to the budding young artist.

What you need to keep in mind is that there is never just one way to do anything.

Thanks guys.  Some food for thought.  It's important to me that my own artwork goes on this, so I really don't want to turn it over to an airbrusher.  Does anyone know of a service where you can submit artwork and then they can perhaps turn it into a transfer? With metallic paint and all?  If all else fails, would it be smart to practice painting on one decal, but do the actual painting on the final decal after it has been adhered to the tank?

Paladin, I have seen your daughter's artwork (the "quick sketch"  sheesh!).  She's incredible.  Tell her to stop being her own worst critic.  Right now!  I started doing portraits for our town's folk at her age and made enough money by the time I graduated to go to California.  She's got a money maker at her fingertips whatever she chooses to do in life.  Pretty nice back-up.

I have regular artist frisket, but will this work on the metal?  Do I need to order a special tape paper that I can x-acto  out the image?  Once again, thanks for the support and advice.  I found a book on Amazon called "Automotive Cheap Tricks & Special F/X"  that I might invest in, if my practice runs don't pan out.

I would suggest the stuff that is made for cutting sharp images (don't know how complicated your design is going to be). I thought the stuff was still called frisket no matter what form it came in

A tip that is probably in every book is to make sure that you coat the edges with clear before you paint color so the paint doesn't leech under the frisket (spray away from the edge to keep from forcing the paint under the edge.