I do not conduct any training either for RFI's and RFP's. I must say I have a support group that takes care of Ariba Buyer Support, and I incorporated Sourcing in there training. They take technical calls for sourcing events also.
Honestly, we do not receive very many calls when we publish RFI's and RFP's. I keep my templates simple, and it's pretty much self explanantory.
I also send the suppliers an invite email, describing how to login and where to find help if they require it. I refer them to the Ariba tutorials available in the Help.
As for auctions, I do conduct online practice sessions with all the invited suppliers 2 or 3 days prior to the actual auction, This permits the supplier to familiarize with the auction GUI and the options available to them. In the practice event, I incorporate all the established rules that have been built in the real auction, so on auction day, there is no suprises. I find conducting a Practice auction (usually lasts 1 hour) works quite well.