I actually just did this with 1/2" acrylic, sign is 168" X 104" so quite huge.
1. Figure out which studs you are going to use. For me I used 1/4-20 X 3".
2. Get a tap and die for that size stud. Also a drill bit with it.
3. Make your artwork at scale and randomly place dots where you want them. Make them the exact size of the hole you will be drilling.
4. Copy that image and reverse it, print and cut them out of vinyl or anything with adhesive.
5. Apply the reversed pieces to the back of the acrylic letters.
6. Drill and tap each one of those dots, you can use a drill bit collar to get the correct depth. Be accurate.
7. Print the non-reversed on brown paper (it's cheaper, you can get a 48" X 600' roll online for like $70) Just print the outline and dots.
8. Once everything is done, remove the vinyl on the back of the letters and put the studs into the letters.
9. Sit them on a table over the template with the studs touching the template. Verify all holes match, if you are 1/8" or more off on some holes, trace the stud around it, this way went you drill the holes through the template you will use the accurate marks.
Presto that is all!
EDIT: Also you can buy studs cheap on grainer for like 15 cents - 30 cents each. Very cost effective instead of trying to make your own.