Has anyone considered that the best rating service is THE BOOKMAKERS OPENING QUOTES.?
If roughly 70% of winners are in the 1st 4 favs and the pro,s bread and butter is between prices 2/1 to 5/1 why not just concentrate on these horses.
The prices you achieve will depend on your quick judgement on what price to accept and the ebb and flow of market forces.
Sometimes the simplest things are the easiest.
Cheers.
darky.