"Clean your thermometer with this one weird trick!"
At about $6-$10, I consider them disposable after awhile. Also, I've never successfully cleaned one but I might try Travis' razor trick.
Also, analog dial thermometers don't stay accurate forever, and will eventually read too low. Successful preservation will eventually work against you there.
Or you could invest in a digital thermometer set with two probes like the Maverick 732, 733 or the Thermoworks Smoke.