I may be wrong, but I think this was discussed a while back. Not sure though. Try a search. Good luck.
[color:blue]1969 Mach 1-in restoration</font color=blue>
[color:green]I got my stang on April Fools day. I wonder if that means something....</font color=green>
Although involved, it is not all that difficult. I like to make several measurement points and then use some 1/4 inch 3M Fine Line low tack masking tape to stretch a nice straight guide line along the length of the car. I double check by sighting down the car from rear to make sure the guide line is not lopsided.
Using lukewarm water with a small amount of liquid dishwashing soap (a couple of teaspoons), I sponge on a liberal amount to the area to be striped. I then position the stripe, using the guide line tape as a reference point. Using a nylon squeegie (bondo appliers you can buy at Walmart, Pep Boys, etc), I carefully work out any bubbles from the center of the stripe out to the edge, using a towel to wipe off the excess. I let the stripe airdry for a few hours before pulling off the protective backing, making sure you pull the backing almost parallel with the stripe itself so as not to pull it off. You can use a hair dryer to speed up the drying process.
In the future, try not to get wax on the reflective stripe as it tends to lift the edges eventually....
Not sure what year/style your referring to. I found the 70 a little more difficult and involved but pick a cool day and put the car up on level stands or a lift (I like to sight down the side to line up the long stripes.
As already mentioned water with a very little soap, mask the stirpes into place along the top edge and start with the big stripe first.
Make sure you get a chance to look at some original cars (if you care) first beacuse the stripes often had little oddities as how and where they were place. Example 70 stirpes varied a bit between the Dearborn and NJ plant installation