In my experience, multips don't have the kind of excruciating-contractions-two-minutes-apart-for 40 hours-that-don't-produce-any-kind-of-cervical-change kind of labors that primips have. I have also not noticed as many problems with descent in multips with posterior babies as with primips (in some primips, babies won't come down at all until they turn, whereas multips' babies descend just fine and sometimes turn at the last minute or not at all.
I work as a midwife and as a doula. As a doula OFP and doing lots of maneuvers to turn a posterior baby are really, really important because of the nature of the hospital experience with its time limits, negative comments of the hospital staff and threatened interventions.
One thing that my preceptors did that seemed to work a lot of the time is to try and stop a labor which has started and has the hallmarks of a posterior labor (with the exception of PROM, which they would not try to hold off labor with) These would include back pain, baby who could be palpated in posterior position, flat or indented belly around umbilicus, contrax close together but weak or not producing cervical change, etc. They would suggest mild herbs/drugs/baths/relaxation, etc. to try and get labor to slow down or stop so that moms could get a break and start over again in a few hours or days. We found, for whatever reason, that oftentimes after that break, labor would begin again in a much more productive pattern. One theory that I have about this related to the belief that some people have that one cause of posterior babies is abdominal muscle tension -- the diaphragmatic release and some of the rebozo techniques are designed to get abs to relax. Maybe the herbs or baths are getting a state of deep relaxation that our clients have found difficult to achieve in pregnancy. Maybe the little break allows a deflexed head to reposition itself. I don't know. Seems to work a lot better than the hospital way of strengthening ctx via pitocin, though.
One thing I have decided not to do, though, is to try and get moms out of certain positions just because I am worried that they might cause a posterior baby. (like lying on her right side or on her back). I find that moms often do a lot better listening to their own bodies' signs when trying to labor. If a mom asks for help in trying to relieve back pain or in trying to turn baby, I will often suggest knee/chest, because I have seen it work. It is almost always uncomfortable, but it is a relatively quick solution, usually working in less than half an hour.
Good luck!