dave rangel wrote:
I assume something like this exists, but wonder where to get it, and if it
should even be used for a roof patch.

We have a couple of sealed skylights that are letting in water when it
rains heavily. The roof is ok otherwise.

I was wondering if it's possible to spray on or paint on some kind of
liquid or gel that quickly cures into a continuous transparent plastic
film that will get into the nooks and crannies of the shingles and around
the skylights, and will adhere well to them.

You get a can of roofing cement. It is a black tarry stuff that can be
applied with a putty knife. Cover the edge of the window frame where
it meets the shingles. A better solution is to remove and re-flash the
skylights. How long since they were installed??