Don't use Mesmerist for trans class.
Mesmerist (at Chaos anyway) will only give 2 free stat/skill resets, and you may use him even at 3rd class.
For the free and unlimited version of skill reset (not stat reset, mind), use Hypnotist at Izlude or Prontera. This one you can do as often as you like, as long as you're lv 99 and below.
Hmm.. so Mesmerist only does 2 free skill/stat reset per character regardless of job and/or class status?