Don't tighten the girth to fast. You can tighten the girth before going into the arena then tighten it in the arena then walk around your horse before you get on and tighten it.
Definitely don't tighten the girth too hard or fast. Also you can pull the front legs straight out in front of them and it gives them nice stretch and helps with bloating
Unfortunately, there is no particular technique ... The most effective is to girth in several times. That is to say to put to the first hole when saddle, then to make it walk until the quarry and then to reshift in order to be able to ascend and that the saddle does not turn. Then one last time after the trigger. For when the horse walks or works, it will be forced to empty the air.
I found a technique that works on some horses, is to place his hands in front of the nostrils (leaving space between the fingers), as the horse goes less inspired it will blow more.