When we took them of we saw some rubber filling (dried after 40 years) Now we've cleaned and painted the car, so we want to put it back on the car (a pillar + horizontal part)

and I have the following questions:
- at Realoem its called filling rubber with part nr: 41359058743, when I google it i come up with POLYURETHANE SEALANT (kit) Is this the stuff I need to use?
- if so: how much do you need to put on? do the holes where the screws go in need to be covered, or the whole a-pillar + horizontal part?
- are there more places on the car that need the same treatment?
thanks