I scanned in my signature, used Alt+PrtScr to screen grab it, cut and trimmed it in MS Paint, saved it as an image and inserted it in the right place into a Word Document version of the AUK Entry form (typed in to Word by myself) with the usual details (my name, auk number, address, etc) filled in. This is saved as my template.
When I want to enter a DIY ride I use this template file, add in the missing details (date, distance, controls, etc), save it as a new file and then email it to Andy U.
I've often done this at the last minute without getting the OK that the route is the required distance although this is risky and it'd be my fault for not getting it checked out first if it turned out to be under-distance. Haven't had a problem as most of my DIY rides are reasonably over distance anyway.
Reminds me, need to send one off to Andy with the DIY+Calendar ride for this weekend.
All of this is a small part of the whole approval/validation process though. A DIY Brevet Card still has to go to the Validator(s), recorder(s), back to the DIY organiser and then back to the rider.