This urge surfing thing has been helping me a little bit but the part where you say "nonjudgmental" is what gives me the most trouble because I have a hard time not to get involved with those fuckin urges.
I had a feeling...
It doesn't seem like much, but this part will literally be a game changer for you, as it was for me. When you come to understand yourself, the struggling and addicted 'you' and the potential new you, where you accept and embrace the process.
You're addicted, so what! It won't always be this way, because you're doing something about it. So, if you find yourself struggling with urges, even with lapses, that's simply the 'addicted-you' acting out, and you can kind of step outside yourself and just observe this while it's happening, like a movie.
What does this mean? Think about it, when you're in a cycle, and you're acting out on either of your addictions, aren't the behaviors kind of automatic? This is because you're in habit-land going from the 'trigger' through your ritual until it's all said and done, followed by the shame, etc... But being mindful is the opposite of this 'mindless' habit-land.
So, when you're feeling the urges, step outside of yourself: "Oh, I'm beginning to think about using, I'm fantasizing, planning how I'm going to do that, maybe I'm firing up a browser, maybe I lingered too long looking at this or that picture..." Instead of trying to fight this, kind of just breathe deeply and 'watch' this happening, and don't infuse it with judgment like, "You suck, you bastard! There you go again looking at this or that...!" Instead, ackowledge that it's happening, or what you're feeling (urges, rationalizations, etc...), and just breathe deeply. Don't react for or against the urges, kind of just watch them as you breathe through them.
You will find that the urges (eventually) subside, and if they come again, repeat- hence, urge-surfing.