The only thing you need to really do to keep rashes away from your baby's diaper area is to wash his bum every nappy change and dry it well before putting a fresh nappy on. No powder necessary, it will save you on costs for wipes, and isn't really the hassle you think it might be. Oh just water will do so no need for soap (I only ever used soap wen he pooped).
Take advantage of sinks in bathrooms, regardless of whether you're at home or at the mall. I actually think it's much harder to wipe a wriggling baby clean than to wash him.
Another tip would be to have a set of cloth diapers or towel to dry your baby's bum with, so these wouldn't be used to wash/bathe him or to wipe his spit ups with.
This worked for my baby and works for other Moms I know who do the same!