After 800 drain room casts, about 100 channelblasts and 9 guild quests, I got blue energy aura for my channeller. In the previous reinc, the blue aura took about 600 drain room casts, 200 channelblasts, and 9 guild quests.

If my spell counts are right, it seems that casting channelblasts (channelball, channelburn, channelbolt) is more efficient than drain room in regards of channeller reputation.

The guild quests also give reputation, although no idea how much. This time I also managed to solo even The slap (tm) guild quest, which normally requires either another channeller or at least some other party member.

Spoiler: The trick was to use your riftwalker entity as a party member.