If you're good with sculpting and painting and other artistic skills, I don't think you should have any problem sculpting your own mask.
I haven't tried this particular method of mask making as shown in the video. It seems to me that you'd either end up with a thin mask after brushing on layer after layer of latex, or you'd lose the detail if you tried to make the mask very thick. I've always made my masks by doing the sculpt in oil-based clay, then doing a two-part mold using Ultracal 30 plaster, and then slush-casting the latex inside the mold. It'll preserve the detail, and all things considered, doing the mold isn't a huge time expense when compared with the time taken to sculpt the mask in the first place and then paint it afterward.
The Monster Makers has an overview of this method on their site.
Good luck, and post pictures as you go!