That is not salt secretion from his lower lip.
Salt (snalt) is only passed through it's nostrils.

Looks like caked on food sometimes caused
by chewing on wet or mushy food.

What have you been feeding it?

I would take more aggressive measures than a
damp q-tip. The caked on food (if that's what
it is) will only cause more complications in the
long run. The fact that the lip surface is covered
by it will only causes heat as well as lack of air
to the area in question, thus ... making this area
a good candidate for a bacterial breeding bed.

By "more aggressive measures" I mean an old
tooth brush moistened in a betadine/water solution
at about the color of a light tea. Try to do this at
least once daily followed by a light smear of a
topical antibiotic cream like SSD or even some
triple antibiotic cream that you might use on your
self will do.

John