I have just recently installed a new set of custom made decals on my 20 year old/new steel Miele bike. A Mike Swantak of VELOGRAPHIC made them for me just from the photos I supplied. He did a fantastic job and I'm very pleased with the results. A patient and professional guy, I highly recommend him if you are considering giving a new face to your old ride.
http://www.velographicdecals.com/
My decals were all individually precut into small manageable pieces. I suggest you do the same and install one at a time. They are easier to manage. Throughly clean the frame of previous residue with Gunk remover, whatever. Degrease also. Keep your finger prints off the decal seating surface areas too!
Line up the area that you want to mount the decal. Do it several times. Practise lining it up for perfect orientation. Also line-up the opposite side if there is a matching decal. Dry-run and triple check all clearances with the decals, preseparation. Peel off the back layer and place, working slowly down or across the decal from one end to the other. YOU ONLY GET ONE CHANCE AT THIS CAUSE THE DECAL IS PERMANENT ADHESIVE. You will most likely destroy the decal if you have to re-lift it!
Use soft rounded wood or plastic utensils to burnish press flat and remove any air. I used a small wallpaper/artist seam roller that worked great. Always work from the centre out to the edges. Spend extra time on the edges for a good seal.
Then carefully peel off the last top piece of carrier sheet at a 45 degree angle. Watch that the decals don't lift off at the edges. Use a small exact-o-knife to carefully separate if this happens. Lastly and very gently, roll the tool across the decals once more to establish good adhesion has occurred. Be careful not to snag or tear the new decal surfaces.
Clear coat wasn't necessary as I wasn't repainting and the new decal quality is quite durable. The O.E.M. decals were not clear coated either and they lasted 20 years.
Take yer time. I was sweating some, but the job came out perfect!
(andnowfortheumpteenthboringpostpicofmyold/newbikeagain)