So, I heard that there was a method to separating the Tog(long) and the Thel (short)on a double coated fleece with a drum carder. So I tried it with a Scottish Blackface fleece I had.
Hold the tog in one hand and the thel goes against the drum of your drumcarder as you spin it. The thel is pulled out by the teeth of the drum carder, leaving you with just the tog in your hand. This method gives two types of prep, with 1/2 the effort it would take if you did it the traditional way (combing the long fibres out for a top, and then carding the short ones for a batt or rolags) The down side: my drum has 120tpi. It's intended for fine fine fibres, and not a double coated fleece. As such some of my teeth are bent :( If you have even a 72 tpi drum, then I think you'd be fine to do this and have no harm to your carder.