how much dynamat for g35 sedan?

That would be correct... if the information you looked up was accurate that 112.8 SF is the interior surface area of the vehicle. But that number does seem a bit high for me. Are you sure you didn't read Cubic Feet? That seems more accurate in that regard.

As for a video... I don't know of any but here are a couple of tips for dealing with Dynamat or similar products.

1) Get a heat gun and heat the mat up a bit while working with it. Wear snug fitting gloves to keep the heat out of your hands (especially if you are a bit clumsy like me). Heat the product up and lay it into place. The heat will keep the material pliable and allow it to follow contours well.

2) A hard rubber roller will make it a LOT easier to apply the mat. Think of it as squeegee (sp?) the air out of tint. This will maximize contact with the surface and allow the material to work better. Air trapped = bad.

3) Work in smaller pieces even if the area is a large flat area. I started out with pieces no bigger than 4x8" but now I can fairly easily handle 12x12" with little worry. This stuff is essentially useless if the contact sides fold over each other. Don't worry too much about the seams being an issue. The point of mat is to add mass that will absorb the vibration and/or make it harder to begin to vibrate/move. If the pieces are butted up to each other snug enough, they'll do their job no problem. Cosmetics are not an issue unless you plan on displaying the mat somehow, but that is a personal choice.

4) Buy 10% more material than you need so that way you are sure not to run short and to take into account some areas that you may to cut and throw away some mat to make it fit. Since you need ~113 sf for the vehicle and plan to double layer it, I recommend that you buy ~250 sf for dual layers and to account for odd areas where trimming is needed.

5) BE PATIENT!!!! Particularly if you are new to this, you'll want to take your time to make sure that it is correctly on.

and last but certainly not least

HAVE FUN!

Ganbatte ne!

Thank you so much for the reply. I have worked with dynamat before in my current car, I just wasn't sure about the entire car.

I have another post in the car audio section about speaker brand comparison, if you could read and give me suggestions, that would be great.

Thank you for your reply, and thanks in advance for everything else.

Nick