I won't usually draft a bench spot in the 3rd round unless a RB REALLY slips. Finding a trading partner sounds good in theory, but I've been in some very competitive leagues where only a couple trades get completed during the entire season.
FTR Last year I got Deuce, JJ, Caddy in a start 2 RB, no flex, then when Caddy was at his peak value I traded him for a WR, only to see Deuce and JJ go down on me.