I mostly prefer to spin 'in the grease' but always give everything an overnight cold soak, which removes a huge amount of dirt, even from a fleece which looked clean.
You
can comb greasy fleece, but you need to be sure that the grease is not solid, so as FW says, warm the fleece up if it's cold. And if you're using large combs, as you would for a longwool, you can heat the tines, too, which makes the job a delight.
Some fleeces are just more greasy than others though. Shetland is usually not especially greasy, so many many people spin this in the grease. At the other end of the spectrum, merino is extremely greasy and also extremely fine, so probably would be a challenge if not washed.
When washing, as well as not agitating, my three top tips are:
- always cold soak overnight
- to remove grease, use scalding hot water (grease melts at 72C, so cooler than this will not remove grease) and do not leave in longer than 15 minutes. Rinse at same temperature and do not leave in, either. Rinse several times, until the water is clear.
- use non-sudsing detergent - I use Ecover washing up liquid - and plenty of it
Fleece I've washed myself has been fine after storage, but I have had fleece washed by others that's been horrible - too dry, sometimes a bit brittle. (And wasn't a brittle fleece before washing.). I've put this down to over-washing and/or inadequate rinsing.
If your fleece preparation, be it combing or carding, is other than top notch, it's
much easier to prep and spin washed fleece. Greasy fleece will find out the weaknesses in your carding technique!