I gave up on oven cleaner - too impatient. And I try to avoid chemicals. Don't get me wrong, I really like them (see impatient). I'm just not good with hazardous waste - I don't like the way my roses have been following me around the yard lately
My number one tool is a razor blade in a retractable blade holder.
The scariest part is when you first use the blade and you see the shiney build-up peel off. "Damn, am I peeling off porcelain?". No, that's just the build-up that was stuck to it. Once I got past that fear, I became a scraping fool - in addition to a regular fool.
The Weber porcelain is beautiful and is almost bullet-proof, and the build-up, light or heavy, comes right off the inside of the bowl and lid.
Followed by a light scrubbing with water and a SOS pad. The soap lubricates as you scrub and you can feel any build-up you left behind. Rinse it off and admire your reflection.
Works great on the Genesis hood as well.
For the outside, a wipe down with soap and water, followed by 0000 steel wool. Lightly with the razor blade for tar, paint and other stubborn stuff.
For rust on the other parts, I like vinegar (distilled works) and a tool for scrubbing - Steel wool, wire brushes and wheels.
May have to try Mothers Mag on my legs and pans.
Along with an extra large can of elbow grease and some time.
Then sit back and enjoy another "R", Re-Admire