Don't bother listening to the one's that say you need a diptank for domestics, they would say that after spending all that money. I get a lot of enquiries for oven cleaning even though i don't really advertise for it, so i sub it out, but i am thinking of adding it to our service.
I have tried a few oven cleaners until i have have found the right guy, he is the only one not to use a dip tank, he is self taught and he use's a large tray for the racks. Every customer is over the moon with his work and he can also get through 3 jobs a day easily, 4 sometimes depending on the jobs, so it does not seem to slow him down!