LOL Checkmateking02-the easy way is to buy only kits with decal fuselage bands.
Alas! Unfortunately not always possible or desirable for aesthetic reasons. Painted bands simply look more convincing, I just built a 48 scale He-111 that took all summer and most of the fall and I'm still doing detail and touch-ups. I had to paint on the white fuselage band.
Here is how I do it:
Prime coat the model. When dried and cured freehand paint on the final color needed for the band just a tad wider than the final band needs to be.. Let that coat fully dry and cure. Since the masking tapes will be in place for a while as you paint the final finish, I hand brush a thin coat of gloss coat over the banded area and let that dry before I mask off the band.
For masking the leading and trailing edges I use Artist's Curve tape from 3M (got mine from Amazon-never saw it in any store). It is a thin, narrow and fairly thick stripe tape that easily bends and conforms to irregular curves as in a fuselage. I measure this tape's width and double that measurement to allow for the leading and trailing edge that it will be used to mask.
I take the total width that the fuselage band will be and from that I subtract the double width measurement of the curve tape. This gives me the width measurement of the masking tape to use on the middle part of the band. I measure and cut out two masks-one for each side of the fuselage but short enough to leave the top and bottom exposed. When these are in place, butt up the curve tape against the edge of these masks and slowly and carefully mask off the leading edge of the band ,completely around the fuselage, keeping the curve tape butted against the middle masks and bending the tape to conform to the fuselage curve. Once that is done, repeat for the trailing edge. All that is left is to fill in the bare areas top and bottom with masking tape and you are ready to paint on the finish coat(s).
BTW- If anyone has a better/easier method for painting fuselage bands then I would dearly love to learn it. I am always open for learning about how to do things an easier way.