Rick - I've done that in the past. Used aircraft sealer at first. Worked great but you needed dynamite to get the damn stuff off.
Found that good old Permatex or something like Black RTV worked just as well and I could get the old gasket out, if need be, with minimal effort. Shot the cover with Carb cleaner and wiped well with a clean rag then applied the gasket and goop.
Alternatively, I've been thoroughly greasing the gasket (both sides), let it sit for 30 minutes or so then slap everything together. That works well, too, and I have CB bolt-on aluminum covers (which are notorious for leaking, but these seem OK).
Whatever the heck seems to work!