I'M no expert in this area, but for a lineman who already has the size, even if it ain't all practical size, you should focus on strength training. Core strength, leg strength and your pushing strength (tons of close grip benching) and your overall athleticsm. Being big and strong will get you pretty far, but being big, strong AND athletic and agile will make you excell at what you do. Go see some youtube videos, the channel is Strenghtcamp. Elliot Hulse is as guy who trains and preps football players, so you might learn alot of things from him!