I cut back the grapes today, while we were harvesting, but it’s probably too early, and I definitely went too crazy with it.
Found a good reference for pruning next year
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https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec1639.pd
Basically, each year you choose one fruiting cane to use as the new feeder for the next year. Looks like pruning should be done in the C winter when the leaves are gone, and finished up in the spring.