honestly, just go to an art supply store or a body shop supply store and get:
- sheets of flat masking tape (you can get them in regular paper size if you want to run them through your printer for a complicated design)
- 3m flexible stipe masking tape in 1/8 or 1/4 of an inch. stuff is awesome and what they use to lay out flames on cars.
make a paper template so that both sides of the masking tape come out even. The secret to the rustoelum/brightside method is the sanding, doesn't matter how the paint gets on the tank, just how it is treated between coats. if you wanted a matte stripe or a matte tank I would spray can it with semi gloss, sand between coats, and finish with a buffing machine and the rough turtle wax compound (the brown stuff not the white). it will give you a semi gloss finish that is nice and smooth. Were you going to do the stripes in matte I would use vynil as it is way less time and slightly more reisitant to wax and such which would otherwise shine up a matte paint job.