I would suggest now (late winter) is an excellent time to prune hydrangea shrubs. There is an extension service publication that guides you on pruning tips. See:
For general pruning tips, consider the following:
First cut out dead, disease, injured, weak and twiggy growth.
Next remove shoots or twigs that are growing in the wrong direction, getting out of bounds, or crowding and crossing other limbs.
Finally finish the job by thinning out where necessary for even spacing of branches, ease of spraying, and to maintain moderate growth and good annual flower production.
Investing in a good pair of shears makes the job a lot easier in my opinion.
If you have any follow-up questions, please let me know.