Pet Care Needed

Shadowfax is a 6-year-old Maine Coon mix with long thick fur, I keep him combed out, but his underbelly gets knotted up and I have arthritis in my hands so I can't always get them out. Also, I have not bathed him in over a year, I'd like to have him trimmed up and get his coat looking better. He still has his summer coat , so I would like some recommendations for bathing, coat care, and nutrition if possible, he's prone to hairballs despite using paw gel. He's never been groomed, so I have no idea how he will react to it.