I took the plunge and lacquered the brass. I did a very light pass over the emblem first to minimize the reaction with the old red paint. Even so it did seem to melt a bit under subsequent coats, but it hardened along with the lacquer so no harm done.
I used Mohawk "Lacquer for Brass". I've tried cheapo Watco lacquer on brass before and it instantly discolored. This stuff is much better.
Check out this list of ingredients. That's some potent stuff!
n-butyl acetate, ethyl acetate, propane, pm acetate, isopropanol, isobutane, isobutanol, acetone, methyl ethyl ketone, cellulose nitrate, cellulose ester, alkyd resin solids, polyketone resin, ethylbezene