I used the JDBB, but I bought the 1/2 gallon paint and mixed myself. I, however also have used the JDBB from a spray can when I made a dog carrier that mounts on a detachable rack. It came out pretty damn good. I would think one can could do a saddlebag, but buy 4 just in case.
You will probably still need to prep to get that silky smooth finish but it's doable. very doable. practice
1st coat needs to be light. meaning you need to see 50% of what you are laying it on.
2nd coat needs to be medium. meaning you need to see only about 10-20% of what you are laying it on.
3rd coat needs to be wet. Meaning this last coat goes on thick and be sure to keep your eyes on the spray pattern and see it overlap about 1-2 inches.
Couple more tips:
Start you spray before you hit the bags about 4" and follow thru past the edge the same.
Be mechanical with your arm. Don't fan spray. It causes light application on the end and heavy in the center.
Don't touch minimum for 6 hrs. 12 is better.
"Just put that hammer down and give it hell" -Jerry Reed.