We were having this discussion the other day. I personally feel you should start with doing dips on bars first, to build up the strength do to dips with rings. Rings requires extra balance etc and if you not able or strong enough to do them correctly on bars, you wasting time on rings. As far as technique goes, am sitting here at my desk trying to remember what my hands do... When doing straight dips, I hold the bottom of the ring, lower myself, and then back up again.... the grip shouldnt change. Yes the rings feel like they are getting away at times but thats the extra challenge of doing dips on rings. Good Luck!