Apple Espalier Pruning

Hi all, just joined and looking for a bit of advice.

I've read numerous books and articles about pruning espaliers but I'm finding it really difficult to get a consensus of opion, particularly when to prune.

I'm planning to prune main stem side shoots above the third leaf beyond the basal cluster and lateral side shoots above the first leaf beyond the basal cluster.

I've read varying times to prune from early August to after the worst of the winter weather.

Any advice would be greatly appreciated.

Thanks in advance

Stuart