[Ganchrow]

Is there any proper way to fade a parlay?

Sure. Bet every parlay combination other than the one you want to fade.

What you'll find, however, is that the vig you'd be paying will generally make this prohibitive.

What you should be thinking about is why exactly you want to do this. You need to figure out where you believe your edge to be and then tailor your betting towards that. Chances are that even at zero vig you'd have a superior option to a blanket parlay fade.

[Ganchrow]

I just fade certain people. When somebody posts a 3 team parlay consisting of all -200 and above favorites, I usually just fade all three favorites, but instead of cashing a lot, I barely make crap, since only 1 loses.

At -200 given 4.545% juice the parlay wins with about 25.8% probability. So even if you were fading the parlay at zero vig, you'd be paid off at about -288.

At 10% vig (the same vig as on a 2-team +260 parlay) you'd be paid off at about -471.

At 12.5% vig (the same vig as on a 3-team +600 parlay) you'd be paid off at about -559.

I suspect that these odds might be a bit shorter than you'd like.

I'm pretty sure there is no way to do this other than to lay the parlay on Betfair or some other exchange.

To my knowledge neither BetFair nor any other betting exchanges currently allow user-defined parlays.