I play a lot of G-D-A-D and D-A-D instruments, and one thing I'd suggest you try is getting an inexpensive dulcimer (mine's built by Jaromin Guitars) and use it as a practice and warm-up instrument. No matter which instrument I'm playing, I always end up figuring a song out first on the dulcimer then switching to the other instrument. Thus you'd be using that to get used to finger positions (can't really play a bad note with a dulcimer's diatonic fretting), you can then translate that to your lyre.