According to :
What opinions can I get about slipping membrane or felt into the lap,
under the upper panel and over the lower panel?

If the material is the slightest bit porous, it'll make your leaking
problem worse rather than better. I think it's best to use the proper
roofing sealer goop. Especially if you're lucky and the sealer can
be applied above a purlin to minimize joint movement.

How about sealing old screw holes with aluminum foil tape?
Scary putting Al aganst Fe, but if I go for a temp fix for the winter,
it'd be removed in the spring.

The proper roofing goop wouldn't have the time limit. Foil tape probably
last longer than a year anyway.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.