Does this guy want a black Spiderman outfit, or a Venom costume? (make sure you know which variation he really wants as some folks get them confused and they are different)
In the latest movie, the Spiderman costumes had about 2000 hand-silkscreen details apiece to make all the shadows, muscling and highlights on the fabric match the computer-rendered versions of the characters. I don't suggest you try and do that.
The webbing on the movie costume is latex, hand-painted on and then airbrushed with more texture and color. And on the dark Spiderman outfit, the detailing is silver/grey over black fabric.