Gave up on Motoseal when they changed it in the eighties. Worthless, goes on like hot piss thin JB Weld.
Permatex black on case corners to rubber seals or other gaskets like clam shell motors, RTV high heat red for rubber bits to whatever, grey for cork or case to gasket or water wet work and copper for all your exhaust and extreme environments like a *frenched case seal pocket or wavy muffler flanges. Most stuff gets a steel gasket, my favorites, or NAFT and 518, 400 grit surface prep, shot of carb cleaner, assemble and overnight in a heated area. Case to case or metal to metal 518 only. Clam shell motors like any of the sealers. 518 must be cured first before use! No air is the key. Vac chamber speeds the process. 518 will not hold on a polished surface. If you use a wire wheel to clean the surface, you just polished it. A betting man would wager this is a major problem with so many re-builders of all kinds.
If you stick to this you will have very few adhesion or curing problems. If you do have problems it was most likely you missed a step during your prep. Go get a can of spray on etching adhesion promoter K.I.S.S.
PS
Once frozen sealers rarely cure