Headgaskets Aluminum Heads

The Mopar spray was a combo of soybean oil, Teflon, & cellulose fibers, and the instructions for the new MLS gasket installation was to hang the gasket & drown it till it dripped from in between the layers, which were stainless with thin sheets of Teflon sandwiched in between.
Using Copper spray gasket or teflon spray or paste isn't to "seal", it's to prevent damage to the sealing surfaces as they "itch across" the surfaces during expansion/contraction cycles.