It comes with practise. What helped me (and sometimes still does) is to ensure vertical separation exists before turning one onto a tight base behind another on final. That way, if you've misjudged it, at least you have separation, and you can then sort out the spacing by taking it through the loc / slowing it down earlier etc.
As to a spacing which reduces below wake turbulence minima...if radar are still working the following aircraft, it's easy - break it off and re-sequence. The minima are there for a reason, and numerous fatal wake encounters over the years (and around the world) are why I have no time for the expression "are you happy to continue?" when they haven't been provided with the correct, safe spacing by radar...