Trouble Hooking Up Trailer due to "Gear Slack"????

I am pretty stout and this might not work for you but I can push or pull the tow vehicle the half inch or so that results from "Gear Slack".

Alternatively, I open the pickup door and pick a point of reference. If it rolls forward or backward when I release the brake, I put it back in the appropriate gear and move about one inch in the opposite direction of the roll.