My baby is 6mths old, same problem here. All I am doing is keep replacing his bib, almost every 30mins.
Secondly, I keep cleaning his face with cotton pad(soaked with water) and then applied physiogel Al cream. Then the rashes will gone gradually. This method is very effective.
baby's doctor said I am doing correctly, keeping baby's face clean and moisturized is the most important.
So when cleaning my baby's face, I am just padding on it NOT rubbing his face