Everybody who isn't a power lifter (meaning they want form over function) could easily bulk rapidly just by watching a scale and using portion control. Weigh yourself after the morning bowel movement every Sunday and if you've gone up, great; if not, add 500 calories to your daily intake. Once you see weight going up on the scale stay at that daily intake level. Lift 3+ days a week.
There, you can now add very lean weight.
Most guys just pick some crazy ass high number like 4,000 or 8,000 and eat that daily until they are ready to cut. That's retarded. You want to stay hydrated and you want to have the building blocks your body needs for new muscle plus performance; that's not nearly as high a number as people pretend it is.
Proof? Look at dudes in prison with limited calorie resources or jacked poor-as-dirt dudes in Africa.