Ok. Here's one. Since there have been a few people willing to think a little differently, you might give it a go (for a while, at least!!!)

Look at any races which are Open or above. This includes Open 3yo and races for females. At those Metro tracks which have No Metro Wins/1 Metro Win races etc you may wish to include these as well.

Rule 1) Select all horses which have NO places in the past three runs. Any spell (ie - or X) is ignored; treated like it isn't there. Example 2506 or 5X06. Any horse with 1 place in the past three IS acceptable if all three places add up to 19 or more (0 is worth 10). Example 2081 or 929 or 2X89 or 88X3 etc etc. You'll note that having two places means it can't possibly add up to 19. This first rule will bring "apparent" non-performers to the fore or horses which have only one vaguely "decent" run in three.
Rule 2) Look at past three runs of those from Rule #1 and keep any that have NOT been beaten 10 lengths or more, more than ONCE. ie If a horse has been thrashed twice (or three times) in three runs it is seriously hopeless and even one win/place with two thrashings is "probably" a fluke. It shouldn't stick to this grade.
Rule 3) Bet all that are left which are at 20 or MORE.

That's it!! Here you have horses going round in better grades who have been performing moderately and who are almost certain to be ignored by any kind of person looking for "consistency". Except if the win/place was Last Start or a win Second Last Start you will see few systems pinpointing these horses.Often the win/place will be in lower grades,if recent (hence the 20s on offer), or similar grade if the third or Second Last Start (the subsequent "poor" performance will have scared punters away; hence the 20s).
Your job is to check the beaten margins as this will tell you more than the 3X89 etc about where the horse actually was in the race. This idea is pretty basic but give it a go. Bet ALL the qualifyers. After a while you MIGHT want to quinella or even trifecta them as well (keep an eye on this for a few weeks).
Theoretically, a trainer who's horse is as "hopeless" as some of these will appear, "should" either spell the horse or DROP it (further?) in grade, if possible. That they don't is "suggestive". You may wish to discard horses who's only win/place (if they had one in the three races) or a close-up finish 2 lengths or less) was AT LONG ODDS, on the principle that THAT was the upset/shock improvement you "should've" been on. Because these horses ARE inconsistent it might be too much hoping for two "shocks" so close together. This last is only a suggestion. My advice on this is method..... Bet Small if you are not convinced, but if either Big or Small betting BE BRAVE!!! Cheers.