Actually, the easiest thing is to do the two leves in Uldah for Uwilsyng. If they aren't an option, simply complete another in-town leve (for any job) and this will reset the selection. Hasty Hand the leves since the exp gained per synth is low to begin with. This is the most time-efficient method. That's roughly 300k exp for 99 leves - enough to go from 47 to 50.