Really sorry for the slow reply – just getting back into the forum swing.
I think a general key to success is certainly to look for multiple pointers to the chance of a horse, as you suggest in your post. One thing about Trainer Snippets report is that I’d be careful using the ‘All’ button with filters applied, because different snippets have different general win strike rates.
As an example, I’d expect Race Code to have a few 20%+ win strike rates most days; trainer change could be as high as 35%; while Handicap 1st Run may be more like 14% on 10+ runner samples.
Hope that makes some sort of sense, and do ask questions here. My reply may not be as timely as it should, but it will arrive eventually!!