I have all of my skills capped on RDM except Divine magic. Healing took the longest and it was all from use. Capping Enhancing magic comes from buffing yourself meticulously and soloing. You could bot it too, but if you actually use your enhancing magic as much as you need it to solo on a RDM, you won't have problems.

It does take a while, but it's not unrealistic if you were here for 90+ for aby. I would cap enhancing before anything else when we went from 90 > 95 > 99. Back at release I used to skill up enhancing when I was on the boat going to selbina or on airships when I had nothing else to do or the game was just slow because sometimes this game was just slow.