I think your on the right track Party. Quite few times here I've advocated that through form study, narrow down the winning chances to bet on to 2 or 3 and then bet the horse with the best odds available.
If we back our main choice only, we will often get it wrong. So why not back the best priced runner of our 2 or 3 winning chances? It will win just as often as our own choice for sure!

Likewise with pre-post runners, if a punter backed the best priced horse [or best two] from say the first 4 or 5 pre-post horses, a similar result as above would apply. The result of course is we are getting value as often as possible.

Another and even simpler method to achieve value betting, would be to follow your favorite tipster and back whichever of their 3 tips has the best bet value. It will win just as often as the other 2 will but your getting the best price every time. You might even turn a nice little profit!