I definately think that putting water right at the base of the post will help. I have experience with this. For your hard cases, you need a system for post pulling. I recommend.
Here's what I do... you may have to adapt if you don't have FEL and only 3 pt
3pt carry all for carrying buckets of water
weight on carry all so when FEL lifts rear tires (almost) off the ground you have serious vertical lift
chain post and apply max vertical lift possible without destabalizing tractor
pour water around base of post, maybe several times
use an tractor jack and chain and ALSO apply this to the post with board to keep base of jack from digging ito the ground.. jack adds additonal pressure, perhaps at different angle from the chain on the tractor.
keep pouring water and gently sway tractor back and forth (not enough to break the post) until you prevail.
This will work.... just takes preparation and time.
By the way... we have droughts in texas too... in fact, most of the time it's a drought
