I'm rather late to this post but I work with my shetland sheep's fleece all the time and use a drum carder with 72 tpi also use a 48 tpi. I use Louet hand combs which are specifically for fine fleece. I don't have many issues with the carded fleece except having to put up with my husbands hand shearing methods of short second cuts (which leads to hundreds or neps

)
My process is to skirt the fleece and generally work with the superfine front half only using the back half if it doesn't feel like a brillo pad (black fleece can be very prone to this) and only using fleece thats longer than 2" because I find anything less a real pain.
I'll then soak it in hand hot water with copious amounts of Bio D washing up liquid (bearing in mind Shetland fleece has less lanolin than many other breeds) - no agitation and empty sink before the water cools. Usually I'm dyeing the wool so I'll only rinse once with similar temp fresh water.
I use the lakeland plastics mesh laundry bags and find I can get a whole fleece in two of the pillow case sized laundry bags BEFORE I soak in hot water.
Then its easy to lift each bag full of wet fleece and dump into the washing machine for a short spin. After that I have two drying racks and I fluff out the fleece to help with drying and turn frequently.
Before carding on the drum (and I use the licker) I'll open up small amounts of dry fleece and card away. I'll usually put it through the carder 2 to 3 times and when spinning, something that helps to tame the wool, spray a little water/washing up liquid solution or conditioner, on the pre-drafted length or rollag or however you spin.
You've probably got your fleece all sorted out by now Anke- but I just wanted to share my process of working with shetland fleece. What have you made with it?