With a stiff (dandy) brush and elbow grease is the best way. Nearly all saddles had serge before and that is what we used. Don't attempt to use any cleaners or wire brushes as a quick fix as they won't do the material any good at all and once you've got a hole in it, it'll take a lot to be repaired. Also, don't be tempted to wash it off with lots of water either, you run the risk of it getting lumpier but you can wipe it over after you have brushed it off. You should be able to brush out any sweat and grease marks if you brush hard enough.
Also (will tie in with the night duty then!) I used to find it a lot easier if the saddle was cold (the sweat and grease had dried) rather than straight off the horse if that makes sense.
excellent - thanks for all your help
The plan is to take one set of tack in tonight and then the next set in tomorrow so hopefully it will make the time pass quicker.
I hate the fact that my saddles seem to attract ginger hair no matter how careful I am