- Find the Brewing Machine
- Send the Drinkin' Buddy to the Hotel Rexford
- (Optional) Keep Drinkin' Buddy for yourself
- Follow Drinkin' Buddy to the Hotel Rexford
- Collect your reward from Rufus
Speak to Rufus Rubin in either the Third Rail or Hotel Rexford in Goodneighbor. He will offer you some work tracking down a pre-war beer brewing machine.
Travel to the marked location on your Pip-Boy until you arrive at The Shamrock Taphouse in the Boston Harbor section of the Greater Boston Neighborhoods zone. Enter the establishment and eliminate the Raider gang in there. Go to the upstairs office and kill Gaff and take Shamrock Taphouse Key.
Go down to the lowest level and use the key to open the locked door. Travel down to the basement, mindful of Radroach and booby trapped rooms along the way. In the basement, you will be attacked by Mole Rat enemies, but be careful of ignited the floor. Retreat up the steps to not be caught in the conflagration.
Against the wall will be the prototype you're searching for. Reading the terminal at the entrance to the basement on the counter will give you some insight to its history. The terminal attached to the prototype is an expert one, so if you don't have the ability to hack it, recruit Nick Valentine for his hacking skills. Once hacked, access the terminal logs and release Buddy. Speak with him and either tell him to deliver himself to Hotel Rexford or keep him for yourself. If you send him to the hotel, follow him there. There is a recipe for Gwinnett Lager you can give him in one of the rooms in the bar. Buddy can also tell you a few choice jokes.
Escort Buddy to the hotel, eliminating any hostiles along the way. He is pretty handy in a fight, equipped with lasers and flamethrowers. It's a long walk to Goodneighbor for the slow stepping drinking Buddy, so be patient. Enter the hotel with Buddy and present the gift to Rufus for your caps reward. Return anytime you find a new recipe and give it to Buddy. Every few days he'll refresh his stock.