On tanks I generally try to just get the clear sanded off with some 180 on a d/a and then use a plastic razor blade from innate.com to scrape them off so as not to disturb the finish of the paint. The plastic blades don't last long but they work great and save me time and money by not having to fill and/or prime the areas where the stickers where. I would still recommend priming where the stickers where lightly just to blend away the areas where you sanded with the 180.

One of my most used blocks around the shop is the wonder block by motor guard, I actually have three of them. It's most likely available at your local paint supplier but if not I'm sure you can find it somewhere online and they are relatively cheap. They are firm but have some give to them and the top of them is curved so it helps in slow sloping radius areas.

Found it on eBay HERE! $6.99 plus shipping from Hollywood, Florida so it can't be bad!