Hi and welcome
Congratulations on your second little one!
I'm not sure I have a good answer for how to keep the paci in when you have her upright....but there's no reason I can see you can't adapt the 'textbook' shh pat and pick her up in more of a cradle hold if that is easier. It is up to you whether you want to keep the paci or not really - I'm not a fan of them personally so didn't use them at all for my kids, but they have some advantages in terms of settling (many LOs have a strong need to suck) and also I believe there is some evidence to suggest a reduction in SIDS risk for those who regularly have a dummy in the first few months. The flip side is that they can easily become a prop and many parents find themselves having to replug multiple times during naps and at nights to keep LO sleeping. I'll leave that one to you!
When DS was born (2.5y age gap) I took things quite slowly, working on only one nap a day at this age. It takes them time to learn and you are totally right that you can't just ignore a toddler multiple times per day to settle the baby. For the one nap I was trying I would set DD up with a DVD or similar and a snack, in a safe place, and then concentrate on the baby. I did however have the mindset of 'do the minimum' in terms of settling for the baby - essentially I tried to get him to bed at around the 'right' time, did a short consistent winddown and put him down. Provided he was happy I just left him to it - I never really tried to 'put' him to sleep unless he was struggling and needed help. When he cried I did go straight back and shh pat (we did a shh and head rub with a hand on his tummy) but I always had a limit of say 15 mins or so. If he was nowhere near settling by then I just stuck him in the sling, got him to settle that way and tried again another time. As he got better at settling in bed we could do more naps there as it took far less time and intervention from me, but honestly with a toddler having a baby who could nap in other ways (pushchair, sling, car etc) was far better than having one who would only settle in the crib.
Hope that helps to begin with!