Another thing to consider is that one of the by products of burning LP is water. You now have more moisture in your cooker than before. That will cause more build up as you cook. Since you know it it there, do like CD said and get your cookers up to a high temp and scrape off before storage.
Team: Pyle's BBQ; Yoder YS640; Good-One "Trail Boss" 60T; Homemade rig; 22" Weber Kettle w/rotisserie ring; Big A$$ Rotisserie; BGE-Small; Weber Kettle Gold, Weber OTS, New Braunfels offset smoker.
Saddles BBQ Bistro