Installing High Heat Gasket

spray both the gasket and the rim.

if you spray the rim while holding the can inside the egg, and fairly close to the rim, you won't need to mask off anything.  any overspray on the inside will burn off (it's nothing but natural rubber, latex).  and if you aim correctly, the overspray on the exterior will overshoot and not hit the outside of the egg.  maybe a little mist, but that can wipe off with a rag of acetone (which you probably have from cleaning the rim).

you can also hold a small chunk of cardboard to block the spray from hitting the inside.  just move it along as you spray

or you can use a zig-zag or permatex high temp silicone sealant.

it's all contact cement.
maybe BGE recommends because the spray makes it easy to apply. hahaha
my point was that in spraying it into a cup, it is not longer anything but rubber/contact cement anyway

like buying spray paint, then spraying it into a cup to control overspray.  wouldn't it make sense to just buy the paint in a can?

$13  buys way more contact cement than what is in a can of 77

for anyone reading along, the overspray isn't an issue when you spray the rim from the inside of the egg, and holding the tip somewhat close to the rim.  anything inside the egg burns off.  it's harmless natural latex

goof. hahaha

anyway, the only diff between the stuff in the can and in liquid form is the sprayability.  they thin the stuff with enough solvents that it can be sprayed. seems odd to pay a premium for something not desired

You can also replace your BGE gasket with a Kamado Joe gasket which is a pretty good gasket! check it out here: BGE, Kamado Joe and Nomex Gasket Burn TEST 

I would check with dealers in your local, I found 3 within 30 miles of where I live.

I used a paint & rust remover on a drill to clean it up. Many people have used this technique. I didn't want to use any chemicals.  It worked well.