How do you HP wash?

I think you don't have enough MP. I could start washing only around lvl 80, and I started at lvl 30 too.
You basically put one point into HP and take one point off MP and place it into your stat (Luk or Dex, for you). The formula for minimum MP for DBs should be something like Level * 14 + 365.

So, I use my AP on HP, then use a reset to remove it from MP and place it on a stat - so HP/MP share points?