Diluted powder used to wash clothes could be effective. Dilute it in a glass of warm water and pour on the greased places on the convection oven, while brushing. Afterwards use a hair dryer to dry, and a hard brush to remove residues. Place a ventilator near to the stove in order to avoid inhalation.
I have found that a Mr. Clean Magic Eraser can remove a lot of buildup in the kitchen, bath, etc. Saves on the elbow grease, too. I use it after I have let the cleaner sit for a while.
can I use a lot of water to clean a convection oven
CLR will work well.
The fluids used to dry-clean clothing can remove grease even when water cannot because grease does not react to water because it is a water-resistant substance. However, the dry-clean fluids' molecules have chemical bonds, which removes the grease.
Elbow grease usually does the job!
Sandpaper.
rain and acid wash
Water cannot interact with grease,due to its high surface tension, so when the water is removed from the clothing after cleaning it, the grease remains. The fluids used to dry clean clothing are actually chemical solvents. They dissolve the grease, so when the solvent is removed, the grease is also removed.
Brasso and elbow grease.
use bread and grease
A proprietory penetrating oil on a q-tip. Use a light (sewing) machine oil sparingly to lubricate after cleaning.
Brasso, a clean rag, and some elbow grease.