[knc1]

Last things first: It will not solve the problem.

tl;dr: Its an out of warranty failure.
Often you can talk Amazon into giving you a credit towards a new Kindle in exchange for it.

- - - -

The K4 is the model that is glued together.
Makes it difficult to service but does not make it waterproof, not even water resistant.

A bit of background on electronics and water -
(Presuming the water is conductive enough, and it usually is):

The first failure is due to the presence of moisture disrupting the electronics.
(You described that.)

As that initial moisture bath dries out, it leaves behind the compounds that will become and/or encourage corrosion.
Also, sometimes not all of the moisture can escape (which just speeds things up).
(You described that stage.)

At this point the corrosion components are established, but have not yet grown enough to fatally disrupt the electronics.

The device is put back into operation and it may well work.
(You described that.)

Now the residue of the bath and the electrolytic action of having power on the circuits makes the corrosion grow.
It will grow to the point where the device will eventually fail (again).
(You described that.)

Bottom Line:
Its junk and being glued together there isn't much hope of fixing it.
Trade it in or e-bay it as "spare parts".