Six down, just two to go! And some help please?

Part of me is sad to have just two horse shows left in our season, the rest of me (which has been basking in the absolutely wonderful crisp weather we have been having) would like for October third to be done and gone so that I can pull Duke's show shoes and hit the trails! Actually, the lazy part of me is tempted to have our farrier put Duke's winter plates on when he comes out this week, just so that I don't have to worry about it in a month!

Now that the end of the season is here (and it's no longer hotter than Hades), I get to really spend time working with Skinny. I've been lunging/lining him about 15 minutes a day, with the plan to work him up to 30 minutes before I try jogging him. Sometimes I put chains on him all-around (he's barefoot) to get him to work his legs more and build up the muscle he needs, but he still seems to be weaker in his front-end .

Does anyone out there have any tips for me on building up a rescue horse? I know slow and steady work is the way to go, and I am planning to start using ground-poles to help work on his coordination, but is there anything more I could be doing? He gets fed a good solid grain that is high in protein (14-16%)and fat (8-10%), plus lots and lots of good timothy hay, and a mineral block. We have added corn oil to his feed in the past, but now that he is no longer ribby I've stopped adding it.

Ideas people, I need ideas please!