Well that depends on if he is a breeding male, or a castrated one. If he is a breeding male, then 10 years is a great age. For a castrated male, if he has been treated reasonably well and looked after, then he could live to be as old 17-18 years.
For a bath, I have an adult breeding male who weighs 23 1/2 stone, and I wash him sometimes! Tie him up, using a collar and lead, or a collar and strong rope, to something strong. Fence posts are always good! Pour a bucket of warm water over him, shampoo him with whatever you want, horse/dog/animal shampoo- even human shampoo. I would steer clear of washing up liquid as his hair obviously isn't in good condition and washing up liquid is quite harsh. Rinse him off with a couple more buckets of warm water, and finish off with a cooler rinse. You could rinse using a gargen hose if you want to, it makes life easier. Bear in mind, you probably will get wet yourself unless you wear waterproofs.
Beth