Great news, you've done welt getting it running nicely.
The brake do take some getting used to but I could virtually stand my Auto-Sleeper on its nose if braking hard. The Jennings coach built, however, was a different matter and as you've found out braking from reasonable speed took planning. I fitted a servo which improved things dramatically but it might just be the shoes, new ones use a harder material than originals so it would be worthwhile seeing if you can get hold of some new old stock items, also make sure the double acting cylinders on the front are free to move on both pistons with no leaks.