I knew about (and have used) the temporary method, but want to know more about the permanent method.
I'm not quite sure I understand what you mean by "temporary" and "permanent" methods. Abilities gain experience and grow either automatically (by passing checks) or by manually pouring Insight into them on the character screen (1 point of Insight = +5 experience points to chosen Ability). In the latter case, you need at least 1 (or more) Insight points in the "Inspire" column for the clickable button to appear. Otherwise, the button there will be gray with the inscription "No Insight".