How do you best make use of it and how do I maximize the benefits to the players, if any?

Adjust your manager and roster settings to maximize the number of players that play in a game. I use tandems and low pitch counts (10 for all non starters) for pitchers. For position players I have my def repl set to replace after fifth inning if winning or losing by 1. 

It seems to be 'games played' vs ABs and innings that means something here based on the mentor advice I have gotten. But someone else may have a different opinion on that.

There is a point where it doesn't matter and I'm sure none of us know for sure.   I play the hell out of my legit youngest prospects, less for the older prospects and give my veterans 10 AB, 3 pitching appearances.

Same here. Major leaguers get 3-5 starts, all pitchers 40 ptches max, player rest starting in 5th inning ahead or behind, defensive replacements.

I make sure my best prospects get at least 25 at bats or 5 pitching appearances. I find ST gives the best ratings bump.

Still figuring out the rest. I've heard people say that ST will slow the aging process in vets. I've also heard all players have a set number of at bats and innings in a season before they fatigue and I've heard spring training burns those. I don't know witch.