If your large your fearful pup does not enjoy baths, one of the best things you can do for him is to give him a bath as often as is necessary. Though in bathing him often, you may not go through the entire bathing process each time. Some baths only get him wet so he can feel the water and go through the motions. Other baths will require more time because you are bathing him with shampoo and rinsing him.
Try the repeat and treat method when brushing as well if your big guy is fearful of this grooming task. This might mean you don't brush his entire body every time you brush him but introduce the brush to certain areas of his body by showing him the brush, letting him sniff it and giving him a treat. Once he's been introduced brush on a certain area of the body, give him more treats. Wait until the next session to brush other areas of your pup.
Ear cleaning needs to happen every week or two. If your big guy is fearful of having you touch his ears, touch them often. Even when you are not cleaning his ears, pull on them, tug on them gently, lift them and look inside, and stick cotton balls in when you can to wipe them clean. Every so often use an ear cleaning solution to get in there for a thorough ear cleaning. Be sure to treat him every time you touch his ears.
Oral health is not a favorite grooming task for many dogs. If your guy is fearful he's probably not going to want you messing with his mouth very often. For you, this means try to do it as often as you can. Again, you don't have to brush his teeth every single time you touch his mouth, but touch his mouth often and introduce a toothbrush with dog toothpaste on it so he knows when you're brushing his teeth you are not causing harm. Be sure to treat as well.
At some point, your large fearful dog is going to need a haircut. At first, you might need to take this in sections as you did with brushing. This might mean you only cut his tail fur one day or his leg fur one day. Take some time and get him used to the tools you use and what they do to him before you tackle grooming his entire body at once.
Your large dogs visits much of his world with his paws. His paws are going to need to be cleaned and his nails will need to be cut. If he's extremely anxious about this task, feel free to cut one nail at a time over the course of a day. As with all other care, be sure you allow him some time to explore your grooming tools and give him a treat during the procedure.
Repeat and treat throughout all grooming tasks to make him more comfortable and build his confidence. When your big guy understands the tools you use are not going to hurt him and the procedure you use for grooming is good for him and rewarding, the easier grooming will be on him.