Wear gloves, wash yourself and your clothes afterwards and sanitise any tools used before you put them back in your van.
30 mins drive away and all you're going for is a single mattress clean? Did you try to sell them something else so you can actually make some profit out of the job? In cases like this I'd give them a rather inflated price for the mattress on its own and tell them I'll do it for half that if they have some other work done at the same time.
The problem with mattresses is the sheer density of the surface you're cleaning. You need some absolutely monstrous lift to try to draw air through it so you can extract it effectively.
The last bogging mattress I cleaned, I connected two ninjas up in series to give me a four vac system. Could've done with steel hoses as the normal ones start to collapse with all that vac lift :

I managed a reasonable result using a good old soak with M-Power for the genral yuk, and a post-treatment with browning prescription for all the pee and "gravy" stains

I know what my own mattresses have gone through in the past, that's why cleaning other peoples' isn't my idea of fun
