When you first brought Rambo home, you thought he looked like he was going to grow up to be just like his namesake. You know, buff, and with a take-no-nonsense attitude. Instead, Rambo turned out to a wonderful mild-mannered pup who take orders easily and doesn't seem to mind being told to do just about anything, including taking a bath and being groomed. Keep in mind, though, that just because Rambo is submissive in nature, it doesn't mean he won't still be a bit on the skittish side, especially around the tub or the tools you need to use.
The simple fact is, most dogs don't really like being groomed. It's too much touchy-feely time and involves things like being brushed and bathed. Rambo doesn't seem to care what he looks or smells like, as evidenced by the other day when he came home smelling like an old skunk. However, you should give him a good basic grooming once a week and bathe him regularly. Check with your vet to see how often you should give him a full bath if you're not sure.
Grooming a submissive dog can be very easy as long as you take your time getting your pup used to the whole process. With a little hard work, the two of you will soon be enjoying an amazing opportunity to bond with each other.