For dub fronts wat u need to be able to do is either do them on tramp or from tramp into foam pit. If u can do this then just huck it off a 45ft or bigger table in the park u'll prob land first or second try i landed it second try. Otherwise if u have powder even better. They're pretty easy just huck it and don't freak out. If u freak out u r fucked. Once one of my ski popped off on the lip because i set it a bit hard and didn't have my dins high enough but i didn't freak out and i just landed on one ski and then slid out so it was fine. Be comfortable in the air... thats the key
My 2 cents
I coach trampoline, and I have taught alot of double front flips. I know it's not skiing but I'm assuming its very similar. If I were to try one on skis I would go through these steps.
1. Make sure you have them down on trampoline.
2. Make a good size pow jump. The bigger you can make it while keeping it comfortable to hit the easier it will be as you won't have to throw it as hard and have an easier time be able focus on what your doing and where you are in the air.
3. Start with singles. Do a bunch get a sense of how much air time you have and visualize how hard your going to need throw.
4. Once your comfortable go for it. Remember it is a blind landing trick so stay into your flip until you can see the ground again. Doing them off cliffs into water and tramp and other stuff I like to get a quick check as my stomach is coming flat to the ground this lets me control the rest of my flip and put it to my feet. Another trick is when you have lots of air time and aren't super hucking you can look under your arm pit for the ground.