Is there a quicker way of selecting an item instead of having to navigate through your items to use it?
You can set quick buttons for the key items you frequently use. For instance, this thread is related. Here is how you do it:
Go to your bag and select the key item:
You will then find the
Then depending on what items you register first, you will see them appear whenever you press Y:
Here, I simply need to press right (on any directional pad) to access my Super Rod.
[Sorry about the bad quality of the images ^^;]
There are a few options for you although you cannot quick use every Item.
Apart from that I don't really know any method of quickly using an Item.