I used sudocreme but LO has only had a touch of nappy rash twice and it cleared it up in no time. I only used it when she needed it. If you get a Bounty pack, there is usually a sample in there, and it does go a long way.
The midwife did say at antenatal that if you are using disposables, the cream can clog up the layer that soaks up the wee, so can actually create nappy rash. I've no experience of disposables, but that was her experience. I think plenty of time without the nappy on is the best way to avoid it.