I use a Peak focusfinder and stop down to my preferred f-stop for exposure. I used to use a blue filter on my older LPL focusfinder, as described in Gene Nocon's book, and found it actually did make focussing easier for me.

If I have to use a small fstop, I'll focus a stop or so above (so I can see the grain better) and then stop down; but these days, my exposure/processing/printing technique is pretty standard, so it's rare that I need to use this method - usually it's saved for my earlier work.