Firstly, sitting in a wet nappy does not cause nappy rash as fresh urine is sterile. Nappy rash is caused when stale urine comes into contact with faeces producing ammonia, which burns the skin. The reason that we associate real nappies with nappy rash is because disposables have an absorbent gel and supposedly this process cannot take place. However any carer changes their baby as soon as required and that is whether you use a disposable or reusable nappy. Bear in mind that there are other types of rashes too.
To prevent nappy rash whether with disposables or reusables, we recommend to ensure that the entire area of skin that was in contact with the nappy has been washed. If you're truly green and would like to save money, why not use wipes made from an old flannel or cloth with warm water? Still, if you'd prefer disposable wipes, make sure you steer well clear of any that contain alcohol. We recommend Jackson Reece, wipes which are dermatologically tested and hypoallergenic. If there is a rash, apply a good cream afterwards that will form a barrier on the baby's bottom.
Don't use barrier creams all the time as it prevents the skin from breathing and makes it more sensitive, which in turn increases the chances of your child developing nappy rash.