Try not to pile a bunch of calories in a few meals. Break it down into about 6 or 7 meals during the day. Pick times of the day where you know you can take 5-10 mins to go to the side, heat it up and eat. Make sure the meals are clean, not pizza 6 times a day. Brown rice, Grilled skinless chicken cut up and some stir fry mix is pretty good. Replace the chicken with Fish whenever during the day. Try and throw a potato in if you can. Utilize different spice as well to keep the same meals each day interesting and new.
Each Day I have the pretty much the same food at the same times and you will get into it and enjoy it after a few days. It does start off a little annoying but once you get to throwing extra stuff in or different flavors you will learn to love it.
If you have 6 500 cal meals a day you will be at 3000 which no matter what your size is going to add mass in some form. Good Luck!!