I've had decent luck using battery terminal spray... goes on like a really thin red translucent varnish. seems to keep things coated and corrosion free.
If you're getting leakage around the posts that much, I wonder if your battery is damaged or defective. Seems like even with poorly maintained posts it should take many months to get any significant post corrosion.
...unless maybe are you dripping acid all over every time you check the water?
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