While adding mass it's going to be hard to not add fat. You can keep it at a minimum by tracking your macros, progress and doing cardio. Also depending on your body type will indicate how often and much cardio you should do.
This. It's very difficult to add mass and not add at least some fat in an absolute manner. What I mean by that, is if you gain, say, 5lbs of muscle, you'll probably gain at least some marginal amount of fat as well. With that said, if you take your time to figure out how to minimize the fat gain while in a caloric surplus, you can end up looking leaner, or even having a lower body fat percent even if you technically gain a bit of fat, because you gained more muscle than fat. This means that you can't go all-out crazy bulking by eating anything and everything in a huge surplus, so you may not pack on muscle quite as fast as possible, but you will minimize fat gain much better, which helps you not have to constantly yo-yo between bulking (and gaining too much fat) and cutting (and losing too much muscle). I'm not sure what supplements or other stuff you're using, but I always like betaine, whether I'm bulking or cutting, as it has research showing it can improve lean body mass as well as reduce fat, making it a perfect addition to a lean bulk IMO. Creatine is another staple too (I get both from PowerMax XT). For someone who is natural, I take every advantage I can get. Of course, proper training, diet, and recovery are undoubtedly the key factors, but supplementing them with some supplements can help you get past a little obstacle. I've always been a fan of a more moderate approach to bulking for most people (those who don't have a crazy-fast metabolism) and not bouncing between drastic extremes of caloric surplus and deficit. I know people who are always either bulking or cutting, but never really make any progress at the end of the day.
