I've got a venus grape vine that I've let just grow however it wanted the last two years so that it could get well established. This year I plan on pruning it to make sure I get just the branches I want out of it.

My question is as follows:

Given that the vine is now dormant and hence the proper time to prune in general, when would be the best time to do so if I want to attempt to root the cuttings?

I suppose the answer will depend on what it takes to get the cuttings to root. I vaguely recall seeing something about taking cuttings early in the winter and putting them somewhere sheltered and cool (like the crawlspace under the house) in plastic bags and forgetting about them until spring. Is something like that what it would take, a couple months of leaving them alone before they'll root (which would mean prune now), or would it be better to prune closer to spring when the vine is waking back up since it'll be in the growing mood?

I'd take cuttings for rooting 2-4 weeks before growth begins. Then they may need to be buried or stored in a cool place until rooting. It depends on whether you can control temperature or are reliant on nature, they need warmth to root rapidly.

I'm not an expert on rooting grapes but have done it many times. Usually by just planting them where I wanted a vine, covering until spring, and then uncovering the top bud. This works but there are ways that result in much higher % takes.

The key to rooting them is getting callus formation first. This works best at warm temperature, just the right moisture level, and rooting hormone. The cutting needs to be fully turgid but not wet. Some experts callus them in moist sand. This months Good Fruit Grower has an article on rooting grape cuttings.

I've never used rooting hormone so that's not essential.