It seems to me that the decals are printed on sheets from http://www.microscale.com/trimfilm.html

As I mentioned earlier I do not make them by my own. The decals are made by a one man enterprise in germany. But is is definitely stuff from the US. The decals come on sheets in US-letter format which is totally uncommon here in europe. So the url above might help.

That's the way I do it:
1. create all the graphics and labels and signs (not the insignias, too big) with CorelDraw or something similar
2. send the file to the manufacturer and check with him if everything is okay and looks the same as well as on his computer as on yours (then order, wait, receive....)
3. cut out the decal close to the border of the graphics/labels
4. apply some Micro-Set liquit with a soft brush to the place you want to place the decal
5. hold the cut out decal into hand warm water for about 10 sec
6. slide the decal to the place with the Mirco-set and align it
7. use a paper towel to remove excessive water/Micro-set
8. apply some Micro-Sol to the decal with a soft brush (you can also do that to a decal which is already dry), the decal will wrinkle horrible, but it will sink into every irregularities and will be flat after few hours. That step can be repeated several time. DO NOT touch the decal while it is wrinkled
9. when dry, it's time to apply the clear coat of your choice. I use 2 component automotive clear paint (glossy or dull). After that step the edges of the decal actually becomes invisible.
10. weathering/scratching of a decal: rub the coated decal with a polishing/rubbing paste (it feels like mashed potatoes) and stop rubbing with your fingers when the decal looks as desired. At last a final clear coating is necessary.

Granted, many steps, but the result is really cool. See the elevator of my Mustang below and a service hatch in the next posting.
The way I make the dirt in the panel lines and around the rivets I allready described here in rcuniverse.