I have just finished with football, baseball, and softball team orders. Many of them I had to make jerseys. Numbers can be very tricky. So I tried royal icing transfers for the first time. Worked out great. This is how I did them.
Print out the numbers black on white paper. The font I used was Varsity Regular. I find a lot of my fonts on dafont.com. You will need to play around with the size to see what fits best for your size cookie. I used a 36 font and it fit on a 3.5″ shirt cookie. I bought the cutter on eBay.
I prepared 2 bags of royal icing. One thick and one flood consistency. I used 1.5 PME tips for both.
Put a sheet of wax paper over the print out. You will be tracing the numbers on and letting them dry. These are called royal icing transfers. You can adhere the numbers with royal icing later. I outlined the number first and then flooded inside. The outline will keep the royal icing inside the lines. If you find that your icing is too thick to pipe you will need to add a little water or corn syrup. Try using a spray bottle so you don’t add too much water. Adding corn syrup also helps if your lines are breaking. This will help to smooth out lines.
For these I pipe the outline close to the paper. Make the sharp edges as much as you can to get that varsity number effect. You can also use a toothpick after and bring out the corners. If you mess up no problem, do it again. The numbers will be very fragile so be careful when handling. Pipe a few dots on the back of the numbers and press on. Make sure to put enough icing so they stick. You do not want them to fall off after all your hard work. I recommend using the color of the jersey for this. Icing may come out the sides and if it is the same color as the jersey it will not be noticeable.
Give it a try. Let me know how they turned out.