From our experience;
When doing insides you need to consider that cars will be in your way no matter what they say. So what you think will take you an hour will take you two. You also need to be very careful when it comes to working around cars. Scratching or being accused of scratching a car can be a costly situation.
So inspect all cars before you start and look for any defects. If there are some then note them, a photo on you mobile phone is good.
When staff see you do this it will make them less likely to blame you as you have evidence that the damage was there before you started.
The same applies to cleaning outside.
Inside is done trad. We use step ladders to reach the top inside windows.
You will have to work around customers - they will always come to see the vehicle that's parked next to the area you are working in. Be prepared to move away to another area and come back later. To cover yourself, ensure you have visible warning signs.
Above all, make sure your insurance covers you for items you are working on. If you or your ladder slip and you damage a large pane of glass, that glass is very expensive.
We have a used car showroom we clean, outsides once a month and insides when needed. Its great doing outsides as we can get started early in summer before they open up or after they close in the evening. The business has 2 sliding door entrances, so we blade the water off of those after we have washed them. We do the outsides wfp.
But you will always be up against their car cleaners. They wash the cars down and usually spray tap water over the windows you have just cleaned.
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