Agree with mm, you're going to have to spray one area at a time to determine where the water is coming from.
I believe the 28 is deck stepped, I get some water through the mast on my keel stepped. Not much I can do about that.
I had a few other leaks that I went hunting for when I purchased my 34. The two culprits that I found and remedied were the Cabin top rails. I removed them, drilled a larger hole ( no larger than the base of the rail circumference dug out any wet balsa, repotted the holes with epoxy
and and remounted the rails.
The other source was the chainplate penetrations. Which I now rebed at least every two seasons. I removed all the chainplates one season, dug everything out and re-bedded.
Now I just lift the deck plates about every other season and rebed from the deck, using 101.
At 1st I thought it was the ports, or the track for the genoa sheet fair leads. In Hindsight, I should have looked at the top rails and chainplates first.
The thing was that the leaks from the rails appeared around the ports and under the tracks. The water travels until it finds an outlet. Might not be your source, but I might start there.