How do i get my rottweiler in a bath?!?

atm we just pour warm water over him in the garden in the nice weather, but in the winter we cant do that, hes not a fan of water and how are we supposed to get him in the bath? our bath is a freestanding one (one with 4 legs) and its quite tall, how on earth do we get him in it?! groomer wouldnt be a good idea as he has a fear of being touched by strangers.