This statement makes me cringe. Your are so very wrong it hurts.
You did not help one “skinny guy” by telling them it’s wrong to do one of the most essential compound mass movements for your upper body.
Barbell movements are more important to a skinny guy for putting mass on his chest then anything else. Yes the medicine ball and dumbbells make for more isolation, and build stabilizing muscles, but this doesn’t mean faster results.
The key for any “skinny guy” to get a big chest is the same as it is for any other muscle. Eat well, and eat a-fucking-lot. Train hard, and consistently, and understand that compound movements with Barbells like Bench Press, shoulder Press, Bent over Rows, Dead lifts, and Squats, are the most important part of you getting big next to what your eating.

Where can we e-mail you for more advice?

First and foremost, your workouts do not become more targeted when you shift emphasis from the chest, triceps and frontal delts (standard bench) to your chest, triceps, frontal delts, back, legs and core (swiss ball). If you understand what targeted means, that sort of doesn’t make sense at all.

Since you now must force your entire body to act as a stable platform from which to bench, you will be unable to use as much weight as you would with a standard bench, and your chest will be bearing less weight as a result. Since your chest is moving less weight, it gets less stimulated, and there is less muscle development.

Also, if the meatheads at your gym are laughing at it, there might be a reason. Those “meatheads” are the guys who achieved what you did not, muscular development. Some of them are blessed with genetics, some with access to pharmaceuticals that most of us wouldn’t want to take; a lot of them are blessed with hard work and the desire to understand weightlifting. These are the guys who understand that the swiss ball does not allow you to lift heavy, and lifting heavy is the way to get big.

There is a lot of information out there on how to get big, I would start looking for better sources.

A formerly skinny guy.