It's fairly common for the cel layers to be suck. 
There's no fail safe way to separate them - you 
always risk tearing the paint off here and there. 
Most people just leave them stuck unless they're 
just barely stuck. Even then, the paint can tear 
unless you're really careful about pulling them 
apart. 

Spacers between the cel and background look good. 
I've never seen them between cel layers, but 
since the cels are stuck anyway... ^_^

Out of curiousity, what series is the cel from?