Nooooooooooooooo! Sudocream and MCN do not mix well, it is very hard to get out without ruining the elastic in your nappies. As ray ray suggests a liner is a good idea. Get some microfleece (NOT polar fleece) from spotlight cut it into strips and put inside nappy.

A cream that i use that is ok with MCN is moogoo. I find it great and wont clog up in your nappies. You can get it online.