Most people go to great lengths in terms of expense and technique to bulk their muscles. An easy method of bulking which would quickly increase your muscle mass all round is to lift big rectangular stones. Simply semi-squat on your feet and lift the weight with both hands and then force the stone towards the chest. To place it on your shoulder, simply yank it sideways and move the body towards one shoulder and let it rest on one shoulder. You should put a protective pad on the shoulder to prevent discomfort. You can then carry it for a distance. With time, you would be able to lift larger weights. Alot of manual labour involving lifting can be achieved thus.