Casting Soul Trap repeatedly on a high level enemy corpse will result in a skill up after only 1-4 casts depending on level difference.

http://redd.it/mc8ha

cool

Works, but monster level didn't seem to matter. Took 15-20 at 90+ even on Giant corpses. If you use the item with magicka un-equip / equip "cheat" as well you can pretty much spam your way to 100, 3 clicks at a time (soul trap - unequip - equip - repeat).

Fun for a while. Double Flame Atronach (FA) with all the perks to buff them feels a bit cheesy (at least at this level). I got to lvl19 before it hit 100 and both Giants and Mammoths go down in no time with 2 FAs up. Can even level destruction spells while they run around chasing the FAs. But already bored. Back to my main sneaky archer.

Nice tip though.