Is it easier to volunteer in USAR?
Yes. When you are Reserve your Chain of Command makes the calls to the right people at the unit you are looking to MOB with, gets all your paperwork together for the tour then most Importantly signs off on you doing the tour.
So my next question would be is how does one transfer to USAR?
There is a form for the transfer like everything else. I know of people who were released from the NG to the Reserves. However to do so would mean you would have to have a really understanding CO. From the little you have said about your unit I don't see them releasing you and that is the key to getting over to the Reserves.
The convo could essentially go like this...
You: Sir, I'd like to transfer to the Reserves.
Captain: Why would you want to do that Soldier?
You: Well Sir, I would like to deploy with xyz and I heard it would be easier to do as a Reservist.
Captain: Dont worry you'll get your turn with us... Anything else I can help you with Soldier? (waits ONE nanosecond) Ok then if that's all DISMISSED!
and there will be nothing at all you can do about it. Of course if you were to move outside of a 50 mile radius of the unit or had some other valid reason then it would be a lot easier to accomplish.