Slot, in the last decade for a while, "value handicapping" was the rage for a while. Guys weer told to make their own morning line, and only bet horses who were overlaid according to that line.
The problem is that what if you think a horse should be 10-1 and hes 20-1 and you don't think the horse stands a chance in the world? Do you bet him?
**** that!!!
I think that method is best used to PASS races. If you think you should be getting 8-1 on a horse who is 4-1, and you really think hes horse to play, just pass the race. That I am a firm believer in.
By the same token if you originally think a horse like scat Daddy is the best horse in a race, and you expect him to be 3-5, and originally think you may wanna spread the race looking to beat him, and you are stunned to see him at 5-2 on the board when they are loading the gate, you make him the key.

I'm sorry but betting 40-1 shots that you think should be 20-1 who you still feel have no chance, is not the way I prefer to go.