AngryPixie, without knowing the criteria of your selection process someone might suggest the distance of race, barrier, days from last start, place/unplaced last start, etc but these might already be in your elimination rules.

With my current methods I have looked at many factors but can't seem to come up at this time with any worthwhile filters - except with my Unitab 100 pointers I will not include any selections resuming from a spell or only have had one race start. Maybe these two rules might be worth looking at if they're not already accounted for in your selection method?