Male, 24 years old
6'0"/178 lbs.
Calories: 2000ish non-workout days/3000ish workout days (2500 weekly average, generally), averaging around 1 g protein/lb bodyweight
3 days/week bodyweight resistance training (ring dips/ring pushups, pullups/ring rows, pistol squat progression)

Goals
Add 10 lbs muscle using bodyweight training and eating clean, low-carb Primal

Question
How do you build muscle mass? What training and eating principles make mass gain possible? I realize these principles are likely very simple, but everything I've seen has them in the barbell-lifting context: "Deadlift, squat, bench, and press + eat tons = muscle mass"

Story
I have stayed steady between 170 and 180 lbs. for a couple years now, but I do not have well-defined muscles. I think the best way to remedy this is to build some mass. My muscles are not large, and losing weight to reveal them would take me lower than I want to go (I'm below the "ideal" weight for my height as-is). When I see people talking about building mass, they almost always are training with barbells.

First question: is it possible to build muscle mass using bodyweight exercises only? I know bodyweight does not progress linearly like barbell training does. I'm a student without access to barbells, but I have a pullup bar, gymnastics rings, and a weight vest that can go to 100 lbs. What kind of training effectively builds muscle?

I know that one early response will be "eat til it hurts," but is that the only variable? Just eat a ton of food, making sure I get adequate protein (1 g/lb desired bodyweight daily)? If so, that brings me to question 2: can I build muscle mass eating clean, low-carb Primal?

Sub-question 2.1: why does GOMAD work, aside from being an easy source of protein and calories? Liquid dairy doesn't sit well with me, so I want to figure out the principles behind GOMAD and see if it works with other foods. Maybe it's the lactose; milk and ice cream are when I tend to have problems.

Sub-question 2.2: why does eating carbs work?

Summary
I am not asking anyone to hand me a meal and training plan. I just want to know how building muscle mass works so I can make a plan to put on 10 pounds of muscle. I feel and look soft, but many out-of-shape, CW acquaintances tell me how lean I am. I disagree; I think I can improve significantly on where I am.

Any help is appreciated.