Dave-mac.
To be honest there is no magic formula or system.
Let me ask you this. Why does it take a franchis operator e.g Oven clean 2 hours to clean what is essentially a metal square with all their potions and tanks.
Because its a load of old ball s**t. If there was it wouldnt take so long.
You can set yourself up for about £40 and do just as good a job. Its all elbow grease.
I do a lot now, all off the shelf products and a tank of sorts that cost £20 from a high st retailer, and my customers are always happy. I even did my own recently (wife is a lazy cow), and she couldnt believe it. Oh and by the way i do it just as quickly as those legendary franchise boys (mugs).
If you want to know more just give me your email add.
Dan