It depends on why you are easing.
If you are turning or there is a change in wind direction (but not velocity) then you dump the traveller (if there is any room to do so).
If there is an increase in wind velocity with the puff and you are already at a good angle of heel then you probably want to dump the main sheet to allow some twist in the leech of the sail. That will dump some wind.
You may find that cleaning the cleat or replacing it with a newer composite one will make it a lot easier to release from the wheel. The older metal ones tend to be harder to release.
You may also find it easier to sit beside the wheel instead of behind it. This gives you better visibility, allows you to see on the windward side of the boat, and gives you better access to the sheets. In wheel steering boats I sit in the same place that I would if there were a tiller and operate the wheel from the side. You can cross sheet the jib sheets (run the sheet once around the leeward winch, then across the cockpit to the windward winch) and have everything in easy reach.
Shape the mainsail w/ your halyard or cunningham tension and your vang. Upwind you're probably going to have more tension on the mainsheet to get the sail shaped correctly. Your vang really is better off the wind.
If you take a gust you're better off depowering by dropping the traveler. That keeps the shape of the main but changes the angle of attack, thus depowering the main.
Let's say you're beating hard and you already have the luff fully tensioned (cunningham on) and the sheet all the way in. The max. draft on the sail is forward. If you ease the mainsheet the boom will lift slightly and the draft will move aft a bit (not as much if the cunny was off) and you don't want that if you're overpowered in the gust.
Plus remember, you want twist at the top of the sail when it's LIGHT b/c that's when the difference in AWA is greater from top to bottom due to frictional resistance across the water. When it's blowing hard, this difference is minimal and you want the sail flat as possible top to bottom. Another reason to use the traveler.
Go out w/ someone else so one person can steer a straight course and the other just plays the main controls.
Trim your main so the tells all flow w/ maybe the very top tell just breaking over the leech a bit. THEN start playing w/ the traveler. As the wind speed increases you'll start heeling more. Ease the trav down and you'll feel the boat start to stand back up. Keep playing like this and you'll see how you can "drive the boat" using the traveler. This keeps your speed up and reduces the drag from excess heeling. Of course if you take a humongous gust you just let everything go!
I will agree w/ Alex on one thing; sit beside the wheel, esp going upwind. You can see the tells better and feel the wind.