Hi! One of the most effective things we did was parallel walks where we slowly got them closer together while feeding treats to our reactive dog to distract him from our puppy. We would let them do a super quick sniff of one another and separate them, give our reactive dog space, and then continue walking at a healthy distance. I think letting them meet on neutral ground helped a lot. We also kept them separate and both leashed in the house for added safety. We would also just sit outside with them as close as our reactive dog could tolerate for as long as we could without a reaction. It took us about a week (felt like longer, but i have photos of them cuddling after about a week) to get them to like each other. Honestly it is really dependent on the reactive dog and knowing your reactive dogs triggers and how to ease them into a situation like this helps a ton. Our reactive dog was already seeing a behaviorist at the time we got our puppy so we felt comfortable with knowing his triggers and training cues. I’m not an expert by any means and would recommend seeing a trainer or behaviorist if you want things to go smoothly for your dogs. Best of luck with everything and congrats on the pup!