They should root in exactly the same manner as shrubby hydrangeas. Check here for previous threads that discuss this in detail.

At this time of the year you are talking about softwood cuttings, with old brown growth not being part of what is used. And it is usual at any time of the year for most of a cutting to consist of stem tissue that is at the same level of maturity. Whether they are softwood, semi-hardwood or hardwood cuttings.

Thank you all for your inputs... I've read also that people leave it over winter, do you know if i need to bring all the cuttings into the house?

Looks like that page gardengal linked to above is likely to have plenty of information. You are asking about fundamental points involved with raising hardy shrubs from cuttings here, surely if you look at those other threads you will find the desired answers.