A long time since posting - busy with motherhood !
If your baby is dribbling and drooling so much that it becomes excoriating and they develop a rash around the mouth and chin, use the following to soothe and relieve: Aloe Vera Gel, Weleda Calendolon / Calendula Ointment and or Nelsons Hypercal. You could also apply a little Lavender Oil neat to the skin.
as well as that try using a cotton bib with a reinforced, thicker neck which can absorb alot of liquid before it gathers on the skin. Tesco supply these and the o+ months bibs do fit older babies. The principles are the same as for nappy rash. Try to keep them as dry as possible.