I've seen some 'cel cleaning cloths' that are 
100% cotton and are supposedly guaranteed to 
clean your cel and not scratch it (I use a 
jewelery cleaning cloth that is also 100% cotton 
and doesn't leave any scratches).  You'll have to 
do a search for them though, because I don't have 
the bookmark on the computer I currently have 
access to.  

Unfortunately, I think that's just for 
fingerprints and such.  Most other people 
reccommend alcohol to remove paint, and if the 
paint specs are only on the front of the cel, you 
might want to try that.  Then use the cel cloth 
to polish it nice and clean.