Ive done it once. I think I used the "make your own dildo" kit that comes in a bucket. It worked well, but it was really tough to do all the mixing, pouring and timing to get it all right without losing wood. My final product is only about 7" long so I had softened up a little more than an inch by molding time.
I'm planning to try it again with the wife's help so I can get a mold at my best. I would definitely recommend trying this with a helper to mix, pour, time and fluff for you.