Okay. So I now have 4 big half barrels with fig trees. I have a moisture gauge thing, but have read some instructions to just water when the soil feels dry to the touch, some that say when the first two inches are dry, and then some say put the gauge all the way in to see what the roots are dealing with, though then i've heard there are surface roots that will be mad if I do that. Which (if any!) is it? The soil is potting soil with a bit of cactus mix, and a couple inches of mulch on top.

i keep all my containers and soils as light as possible. i lift them up occasionally. only water when the container is light, and leave look like they want water. however, in middle of summer when our temp goes over 90.. 100.. i water everyday. not to really water them, but to cool down the container.

other method mentioned to me is just stick a wooden stick into the soil. pull it out and if it's wet, don't water it.

depends on your soil, you also might not want that soil mix to go bone dry. some becomes hydrophobic when dried. keep it moist, not wet, at all time.  

Leaves can talk to us but sometimes they droop or curl at enges only to protect loss of moisture from hot days sun yet the soil is fine and they recover when sun gets low in evening.

I lift lip of pot and can tell if they truly need watering .
Have to use both hands on the big containers such as yours .

Hi jujigirl,
Don't you have an overflow at one or two cm from the bottom of the barrel ?
Normally you should, because if an heavy rain sets in, the tree will start swimming in the barel.
If you do, I would just check the overflow.
With spring/summer temps, I water a watering can of 11Liters every two days or every day.
By now I water a watering can per month, but starting in the middle of April, two watering cans pro week do help a lot.
But ok, my trees are in ground, so the dirt around helps getting rid of the excess of water ...

I have several of my trees (10+) in half whiskey barrels.  I hope you have drainage holes in the side.  IF not, then i HOPE your barrles have large wheels installed so it can drain.  If not your barrel will not drain properly and your barrel will rot in no time.  Whiskey barrels can last 15 years!

I install drainage holes on the side (and one at the bottom middel).  For these barrels use ProMix BX.  It's super light and plant thrive very well.  Make sure to add mini pine bark nuggets to keep the mix moist. 

As for using a moisture meter, I use them religiously!  Just stick the probe in and read it.  Don't worry about watering the plant first.  Picking up pots to see how light it is-- to me is a guessing game.  WHen I'm watering by hand, I want to stick the probe in one hand and water at the same time with the other hand.  I got a lot of plants to water.  Most are on a drip irrigation but some are not.  Good luck!

cheers,,,