I do mine in april. I cut the tips off down to the next pair of buds.
if the bush gets to big I prune down a 1/3 of the stems then another third the next year etc.
welcome to GOY too.

Hudrangeas should be cut back after flowering to allow the plant to grow next years flowers.If you do it in Spring or Autumn you could be cutting away next years flowers.

I do the same as Seaburngirl and it works for me. Welcome !!!!!!!