As a *G or Business Class: in BAH, check-in at the first class section at the end of the airport three hours prior to the flight. Then use the Dilmun lounge which is right as you leave security and passport control. You have to wind between a Chilis (?) and a coffee place and take the escalator upstairs. It's next to Cathay Pacific's lounge. The lounge is pretty good with food and adult beverages, but poor selection of reading material. They also have showers and wi-fi.
In KWI. You must get off the plane. You have the option of waiting in the holding area (no food, water or toilets), but no need to go through security again. Or you can leave the holding area and go to the lounge. There are two lounges in KWI (one for Amex customers and one for *G and Business Class). They have food and nice areas to relax. But NO adult beverages anywhere in the KWI airport and you must go through security again before boarding. There is no separate *G or business class check in, but you are entitled to go to the front of the line.
This new route all the way to BAH on UA great for those of us that live in Saudi Arabia. We leave BAH around 9:00 PM and arrive in IAD by 6:30 a.m. the next morning (and it's often early). The inflight service, equipment, food, drink etc isn't up to the standards of the Gulf carriers like Qatar, Ethiad or Emirates, but the flight schedule, pricing, connections and MP for us is the best.