Wow!

My friend says the back part of her dress looks like a rose. I would like to paint something similar to this on a huge canvas, but those canvases are pricey, and I don't have a clue how to prep my own canvas and stretch it. Use an an old smooth door that is painted white? So how do I prep it to put either oil or acrylic (haven't decided what medium to use) on it? Then I would grid the door and the image, and attempt somewhat of a Chuck Close technique. Image from http://www.arshtcenter.org/_inc/photos/press/hi/1_Flamenco_Festival_color.jpg