When I got my preprinted number plate backgrounds the instructions said to use Windex and it worked perfectly. In fact, it worked better than the product I had been using in the past called "sticker on" that is specially made just for this purpose. The Windex didn't dry as quickly as the "sticker on" and gave me plenty of time to get them on just right. They also sent me a flexible plastic scraper type thing to squeegie (how do you spell that?) all the air bubbles out. I lost it since then and I have to put new graphics on my new Clarke tank today so I just bought a pack of 3 plastic bondo scrappers from Pep Boys for $1.99 and hopefully they'll work as good. One word of advise.... do not use a hair dryer to heat up the graphic, it will make the graphic shrivel up and you'll never get it to lay flat in that spot again.