I've had success doing exercises. It never went away completely but between babies it got to the stage where 90% of the time it wasn't a problem.
Rectocele came after my first baby. I'm now 5 months post partum with second. It improved lots between them and is now worse again, but I'm hopeful will improve again.
I saw a physio first time round and I did a kind of pelvic floor bootcamp approach with her - worked up to doing 10 long holds of 20 seconds and 20 short 1 second holds three times a day. I also did some stomach and bum exercises (pelvic tilts and squats mainly) to improve those muscles. Once the prolapse was feeling better and I had built up strength in pelvic floor, went back to normal amount of daily pelvic floor exercises.
I also bought and did these videos which really really helped when I did them regularly www.hab-it.com/downloads/hab-it-pelvic-floor-exercises-digital-download/
This time around my appointments with the physio are on the phone...! She told me to work up from doing pelvic floors lying down to sitting and standing and then walking. And to vary it up, in terms of length of hold. She said it's the long holds that are most important for prolapse to build endurance.
When it's bad I find it's helpful to kind of reset - I lie on floor with cushions under bum so my hips are higher than torso and I do set of pelvic floors. It really helps!
Also knowing what triggers it (eg for me tiredness makes it worse) and then making sure on those days I do more lying down/no baby carrier etc..
Lying down even just for a couple of minutes really helps too.
Hope this helps!