The hangers should either use the specified nails or the screws the manufacturer recommends. They should have them where you buy the hangers. They aren't meant to be used with any old fastener you have handy. Building inspectors look for them and will reject a structure if they are not installed. An engineer would have to sign off on the substitution to get it passed. I used the screws.
I think you are misunderstanding skew nailing it's simply to knock in a nail at an angle, no need for a power nailer a hammer will do. With one nail each side of the rafter or joist it gives a good locked fix which will not pull apart. If you do use hangers and truss clips as we call them in the UK then do use square twist nails not standard round wire ones.