Never really had much success. Chemical injection worked best but needed to pre-pray. Using a stainless steel brush gave a decent result but no match for chemical only cleaning. Also left the oven dripping a bit so floor needed protection and cleaning. Tried both osprey and duplex machines with similar results, their cleaning videos must have been made with an oven they used once!!
I wish they offered pre sales hands on oven cleaning so I could decide if it was worth it before laying out 2 grand
They are a great adjunct to alkali pre-sprays as they make them more effective.
On the other hand I may just be cack handed.
On the plus side the sight of a cloud of steam rising from the oven impressed the customers.