I know this inquiry is not current but it is something which needs addressed again.
Of course IF the powder coating is CURED on the oven wall it will take more than a vacuum cleaner to remove it.
Some oven walls are stainless steel and if clean will reflect IFRA RED HEAT in the case of this type of oven. If so, keeping the powder coating off of the walls are very important.
So,be sure powder fines will not be flowing into the oven in the first place.