Half our fleet does and half our fleet does not. It's typically only those pilots who actually carry a life raft on board and who will be crossing large bodies of water who need to go through this drill.
Here in Canada there is no specific regulation that says the life raft training needs to be done in water. The student simply has to demonstrate the ability to inflate it and know the safety features of the raft. They highly suggest you do it in water and the one time I've done it, it was in water.
Our training consisted of being in a simulated cockpit which was sitting upright while floating on water. It was then turned over and we had to exit the "cockpit" from under water, inflate our life vest and life raft and get into the raft. We did it a couple of times so that everyone had a chance to do the raft inflation. It is VERY disorientating to start with, but I walked away with a very healthy respect for ditching.
So, I hope that answers your questions of what is the training and do you have to get into the raft unassisted (yes). I'm sure other people have had different experiences with the training too.
Now. There are thousands of types of rafts. The ones we use do not have ladders but it does not take much to get into the raft. Of course, that's in a swimming pool, not the middle of the Atlantic during a storm. Finally, in the real world you'll probably have help getting in, so don't sweat it too much.