I'll share my thoughts after "accidentally" RDing Slinky Dog (meaning I didn't intend to RD it until I was already there and said "why not?") this past week in heavy crowds.
My first recommendation: don't. It's the most chaotic and aggressive RD I've done (and that's coming from someone who routinely RDs FoP and has described on these boards some of the crimes against humanity that I've seen there). My personal theory is that the more wide-open space you have to traverse with the RD crowd, the worse the experience - and there is almost nothing but wide open space on that trek back to Slinky Dog - by way of comparison, RD for FoP becomes relatively tame once everyone is funneled into Pandora's narrow paths - although getting through the choke points are not for the faint of heart).
If you're going to do it, though, here's my experience that somehow landed me on the second train out of the station without any thought or planning whatsoever (just note YMMV): arriving about 45 minutes before opening to find that the crowd was already stacked up waiting to enter the hub even though it was raining, I did the only sane thing and got coffee. Exiting Starbucks, stayed outside the entrance at the top of the stairs (under cover from the rain) as more people had funneled in. Figuring that it was too far back to expect a decent RD showing for SDD (and being stuck on portico and not even on the street), began wondering if heading down Sunset for those rides was the better option. They released early and the human shield of CMs began walking the masses back towards the Chinese theater and into the center of the hub. A small group of us stayed on the right flank and peeled off further right to go down the narrow path beside the Brown Derby (which no one was taking) - we arrived at the end before the main group was even in sight. Now - there were CMs there and they held us - but only until the main group caught up, where we were released to join the front of the pack (which was very easy since they didn't take the group down the stairs by the Chinese theater, but perpendicular to us through the arch into the Disney Jr. Plaza and then turned left to continue beside Ariel's theater). Then it was just keeping up with the crowd. Jostling, shouldering, ankle bites, bumping and the like ensue all around as there's nowhere for anyone to go (and I hope most of it accidental but I can't be sure). Some of us drifted across to the middle or left flank heading into TSL - which turned out okay since the right flank gets pinched on that last hard turn right to enter the SDD queue - that apparently is supposed to follow the umbrellas, which I think I saw more people run into than I have ever seen any group of people run into a row of umbrellas in plain sight. The narrow path did provide some order finally - so then we were all bunched up waiting for the queue to open and could become fast friends commiserating over the experience we'd all just been through - it was magical. I will say that a family at the front with the rest of us had started on the left flank - so the moral is probably "stay on a flank" and don't get caught in the middle (which is good advice anyway to avoid the worst of the crush).
Finally, while there were no shortage of kids in the group and they all seemed to do okay from what I saw, I saw plenty of parents stressed by that experience.
Someone else explained that it's because the majority of people at RD are there for SDD. They don't filter off elsewhere. I'm told the other parks are much smoother. I've done RD numerous times at MK, EPCOT, and AK ( before Pandora), so I'm not too worried. 
