Agree, I didn't throw in PB because I personally hate the shit, but it's a good suggestion for sure.
Yeah, it's the quickest way to add calories to anything ever. A few tablespoons in your protein shake, oatmeal or yogurt, a few tablespoons with some celery, an apple or an banana and next thing you know you've just added about 400 calories and 15 grams of protein to something that was relatively light before.
Aye, I'm the same with milk. Just an extra glass here and there really helps in hitting numbers.
Oh, dude, when I was seriously bulking I was drinking a half gallon of whole milk a day and following a hypertrophy to strength to power to peaking powerlifting workout and put on serious weight. Fortunately during this time, I was also eating an apple and taking a scoop of Metamucil after each meal so the milk didn't fuck me up too bad.