At Smokingpipes.com Adam, Eric, Sykes and I sit around smoking pipes all day. New pipes, estate pipes, pipes from every country, all kinds of tobacco, pretty much all day. It's good times.
This is how we all break in new pipes: We just smoke them. A bunch. Sure, Adam likely has some tricks for breaking in different briar, but ultimately, with but with so much to be done in the day to update our site and help customers, we just don't have the patience for smearing pipe bowls with honey. That and we would destroy our computers pretty fast with 'jam hands'.
If you are smoking a super-junky pipe that's stamped simply with MEXICO or RUSSIA, it may be filled with so much putty that perhaps smearing the bowl with a natural glue shield would be a good way to smoke it without 'burning out'.
But there are so many good pipes being made today. In my opinion, you break in a pipe when it's been smoked enough to smoke well. If it smokes well it was made well. Otherwise you've an excuse to buy a new pipe.