Jeez, you guys can turn anything into a lab experiment! We went from how to get hungry to injections! Joking.
Whenever I have wanted to bulk, I've found that liquid foods are great. One thing to keep in mind is that if you keep stuffing yourself with solid foods you will stretch your stomach. This can be a problem when you want to trim down again as you will have the inverse effect and always be hungry. It will then take a good while for your stomach to shrink again.
I see patients all the time who get around their surgical stomach staplings by drinking WAY too many calories. At first it was a mystery. How in the hell is this person whose stomach is the size on an apple not losing any weight? Well, the answer was they were drinking 10 high fat shakes a day. I'm talking heavy duty cal Steak and Shake shakes!!! Why, because they were told to avoid solid foods for several weeks to allow their stomach to heal.
Anyway, milk is great for this as are protein shakes. The lower the fiber the better as they will pass quickly thru your system and you will be hungry all the time. Cottage cheese is another great one. Solids like chicken and meat will take longer and impart a longer "full" feeling. That is one of the major reasons Atkins works for some people as it is heavy meat/fat laden and they feel full longer. Bottom line, slow absorption = longer full feeling. You are looking for the opposite.
Also helpful, stagger solid meals with shakes as this will allow you a wider span to move the solids thru and still get your cals.