I know this is an old question but wanted to offer some tips.
I think the best prevention and cure for nappy rash is nappy free time.
I never use powders or creams.
Also I would stay away from Napisan as it has chemicals in it.
We wash our cloth in half our normal detergent (for sensitive skin) and then line dry.

My son has only ever had really bad nappy rash on a few occations. And on those occations he was still bathing in his little baby bath... I would give him a salt bath. I was worried that it might sting him, but my mum swears by salt water for a lot of things and told me she used to do it for my sister and I... So how can my mum be wrong??? Turns out for my son a salt bath did the trick. I was not really there for washing him so I just sat him in a tab of salt water and we played.. taking care of course that it did not get into his eyes... But it did not seem to hurt and I took him out of the bath and popped on some powder ( I should find the name for it my mother sent it to me), this powder can be used like cream it is a special nappy rash powder... I am sorry but the name escapes me now.... 

As I have used it up and waiting for my mother to send me another bottle... WIll ask her about it next time I am on the phone with her...

Your diapers have too much amonia in them (I used to run a diaper company).  Soak them for a few hours in vingar and water (like 1 cup vinegar to a whole washing machine load). Wash as usual and you should see a world of difference in just a few days.  Good luck (and feel free to message me back with questions!).

thanx guy i try

Hi There.

    Just wanted to offer you what cleared up my son's. Nappy rash creams are great but they rub off when wet.  Mix some vaseline with the cream as it puts a barrier between the wet and skin.  All the best.

This may sound a little wierd to you, but you should try yeast infection cream.  My sisters mid wife and my doctor recommended it.  Most of teh time rashes are from air born yeast.  try it, it wont hurt and it may get better

Since i assume that you are washing these diapers yourself, you have to be very careful what kind of laundry soap you use. There are special soaps that are on the market for diapers. if you have hard water where you are you may want to add a softener to the wash. When we did cloth diapers, we first washed them in very hot water to of course clean and sterlize them. we put them through a second time to ensure that no soap was left on the diapers. we then dryed then in with a dryer sheet, no scented to ensure their softness. liquid fabric softener can also can rashes if it is scented. also when using creams for diaper rash, ensure that they too are perfume free and this is also an irritant. if the problem still presists, then your baby may be allergic to cloth and yo may have to go to disposible for that you could check with your doctor.