To add muscle mass you need heavy weight. However, heavy doesn't mean the one that you will die from trying to lift. Heavy means the one you can squeeze out min of 6 and max of 8 reps. Note, these should be proper reps - if you're swinging, curving, half-lifting - the weight is too heavy, take something lighter.
You can go the route of first building bulk, and then working on the detail and difinition. For that. I'd suggest hitting every body part once a week with 3 warmup sets of 20-15-12 reps for the first exercise per bodypart and 3-4 heavy sets of 6-8 reps (no need for warmaup sets on exercises other than the first one). I would do 5 exercises per bodypart. Abs depending on your current ab condition.
Alternatevely, you could combine mass building with detail/definition. In that case I would recommend hitting each bidypart twice a week with one heavy one light session per bodypart. Keep the same rputine as above for heavy days but reduce exercises to 3 per body part (warmup sets on the first exercise per body part). Keep the same 3 exercises on the light days but use light weights and a min of 15 reps per set. Substitute the free weights of the 3 exercises with analogous machine/cable exercises on the light days if you want.
Regards
