You can buy nose sprays for babies which is just a saline solution, you can perfectly make them yourself as well. Advantage of buying them is that they often come with a bulb aspirator. When the noses were blocked I used it about half a hour before a feed.
For my youngest I bought a snot pump as she had a lot of airway infections, something like this one;
https://www.catch.com.au/product/snotty-three-electric-nasal-aspirator-1934284/?offer_id=12202015&gclid=EAIaIQobChMIwP_QwZ3g5QIVGB4rCh1RXwT_EAQYBSABEgKA7fD_BwE

you could use a syringe? Small doses of boiled water?