Re:solid food vs shakes
As above, plenty of people use shakes but just ensure they still contain good food. Having a shake of whey/dextrose during the day really isn't going to do you an favours but a whey/casein blend with oats/PB is a decent meal that's quick/easy to consume. It's still all food just blended/watered down to make it easy to consume.
Whey isn't the ideal protein source tho as a meal as it is pretty quickly/easily digested, i'd rather have my body using more energy to digest chicken/steak etc as this equates to a higher metabolic rate.