I've heard references to "break-back " & "piggy -back" trailors, what is the best type of trailor for a 5 to 5.5m Rib ?
I wouldn't bother with a break back trailer, as they don't seem to offer much real advantage, and the mechanism tends to seize solid anyway.
With this size of RIB you only need a single axle trailer. Go for a trailer with rollers, and you will find it's surprisingly easy to launch and recover.
Given good conditions and a bit of practise you should be able to do it solo (I've launched and retrieved a 7.5m RIB on my own a few times, without getting my feet wet), although you'll find it easier with two of you -- one to back the trailer doen the slip, the other to drive the boat onto the trailer.
If conditions are less than perfect though, my top tip is don't try to stay dry!
Bite the bullet and get in the water (a drysuit is a plus here) and manhandle the boat onto the trailer. Trying to tiptoe around, balancing on the trailer is guaranteed to make life difficult. Find a busy slipway tomorrow (bank holidays are always best!) and observe different "techniques" . . .
Do you keep the trailor attached to a car or release it for the final launch ?
If the slipway is steep enough, then you will find that there is enough water under the boat before you start to get your car wet. On a shallower slipway it is far better to use a rope between the car and the trailer. It may seem like extra hassle, but it really is worth the extra couple of minutes effort to set up.