Have Never added any So2 before primary before. First thing done at this point? I guess taking all measurements. Temp, ph, And TA (going to start trying to remember to measure so2 at this point from now on as well)
And then my 1st addition would be enzymes, about 12-24 hrs before all the other fun stuff.
By the time I've destemmed and crushed, I've already had at least a glass of wine. I usually rinse off my 2x4 at that point, sit back, enjoy the results of the my efforts and fight the desire to go and get more grapes the next day.
I'm in the have a glass of wine camp, usually with the friends that came to pick and crush. Of course that is after scrubbing everything including the crush pad. I tried not adding meta last year and didn't have any weird issues.
You add sulfite pre-ferment to kill off bacteria and wild yeast. While the wild yeast can produce off flavors, their numbers are quickly dominated by the commercial yeast, which has been selected to be SO2 tolerant and an multiply rapidly.
Is SO2 needed at crush? I think it depends. If the fruit is in bad shape, I'd apply 50ppm. Great fruit, I would be inclined to add little or none.
Since I mostly only make white wine, after crushing, I press.
No wine for me while still using tools. But I do drink the free run juice coming off the press (and set aside a few liters that go into the fridge for drinking over the next few days).
Side note on sulfite: I have experimented a lot. I have tried none and then either a spontaneous fermentation or immediately adding commercial yeast. For my only red wine the results were similar with different treatments. But for my white wines the results can be very different with sulfite versus without sulfite plus the cocktail of yeasts and bacteria in the must. The differing results are not bad, just different (but chance of wine faults from fermentation was higher without sulfite). And that difference can vary between different grape varieties. For example, I like my Pinot Gris crisp and fruity, which I have found is not possible to my taste and with my grapes without first applying some sulfite and using commercial yeast.
I've been letting the 40°-50° grape temps at purchase act as my protection. By the time it's warmed up enough for wild yeast and bacteria, Im pitching my commercial yeast. (Just the way I was taught). But I am still learning. And scared to mess with future MLF which will now be done on all batches.
Spring grapes packaged with sulphite pads already registered 45ppm free so2 after crush. But if 0 ppm I guess it wouldn't hurt to make a small addition 20-40 free ppm as insurance.