So although - i think the Hulk is rad too -
the GREEN = Vaseline
rose = the flesh
white = plaster strips
Unless you REALLY want to loose body hair, Vaseline, Murphy's soap oil or any other serious skin-healthy oil based lubricant is good.
Apply in the direction of the hair. Do the opposite, and you got yourself a VERY painful "waxing" -but not in a cool way, in a way that just always finds a way of making you look stupid.
If you want the interior mold to be used as a casting mold - then you need to apply a very FINE "splash coat" of light plaster. The finer the splash coat, the finer the detail.
A splash coat is when you mix plaster and water to the perfect ratio at right as the moment the catalyst starts (chemical reaction) you splatter a fine coat of plaster down) the plaster embedded gauze is added onto whilst in it.
Not necessary unless the goal is to cast a cast from the cast - again and again.
This is harder
1) Take the plaster embedded gauze and cut them into strips: 3 recommended lengths:
a) long fat ones for the large spaces in the body (In this case the arms)
b) Long half strips (thin) that can extend down the arm and down through thin parts like veins
c) Take those long half strips and cut a few of those into half band-aid sized strips etc - for fingers and delicate places
Make sure you are crosshatching the directions again and again.
2. once the cast starts hardening you will feel heat. That's because it is an exothermic chemical reaction. It will also increase in weight a touch which if you are doing a straight plaster cast, which often frightens or can even hurt people
3) Where you see the green, add Vaseline . Keep the edges clean and re-lay your arm or what ever back into the cast. Make sure the sides of that first cast are lined with Vaseline so the plaster does not stick to it and you can separate the 2 parts
4) repeat to the exposed hand what you did to the first side to the skin side. allow to dry and pull apart.
5) you now have a cast of 3 sides. you can cast inside and or use the exterior using plaster and or clay to hold the 2 parts together depending on what you want to do