Introducing new mice to an establised colony?

[charcobain]

Hello guys! I have 2 female mice, both sisters who have lived together in my home for around 6 months now, today I'm planning on moving maybe one or two more females into their cage, I am collecting from the same breeder therefor as far as im aware they will also be related to my current mice! I was wondering if moving the newbies into their own cage for 24 hours and then introducing them in a neutral ground will be long enough, or do they need longer? Also, is it okay to introduce all 4 at once? Thank you!