We had 2 St. Bernards while I was growing up. We learned from the first one. These dogs are the Kings of Drool. We trained the first one, when he was a puppy, to pick up a small towel when we asked. This was usually when someone was coming in.
St. Bernards don’t just drool droplets. Their hangover lips can trail a foot-long, thick strand of ugly spittle that can pretty much ruin a pair of pants. So when someone rang the bell or some other excitement happened, we would tell him to grab his towel and he would, thus effectively wiping his own spittle AND muffling that loud bark! It worked very well and was very cute.