Hi Fbirder,
I've been shooting horsebows for the last 25 years, and there are a few things or tips I can probably offer.
Gripping point:
-since you are using a bow, which is covered with leather and nicely bandaged close to the grip, depending on your hand size you can always use the bandage as a reference point. Try to touch the bandage with your pinky finger, to start with. Later on you can loose up on the bottom 2 fingers, to allow a nice follow through.
-nocking point: after a few thousand shots the grip will have a mark on it, if your release is constant. You can use some dental floss or tie a rubber band around the string to mark your nocking point to start with. make sure your nocking point is about 1/4 - 1/3 of a nock higher than a level, so the release will be smooth, the flight of the arrow will be even, and the fletching will not hurt your hand.
I'll put some pictures on the AIUK facebook page, probably that will help.
After a while, you'll just feel the grip, nocking point, so you can remove all aids, and just shoot. Let me know if you'll have the chance to catch up in person, I'm more than happy to show a you a few things
Cheers:
Levente Koricsanszky