When i redo spinner art, i print the art onto Clear inkjet label and stick them onto the white repainted spinners (i use Clear label for just about everything, ie spinner art drop target etc). i usually stick them onto the spinner, leaving the decal slightly oversize so as to make it easier to apply (something to hold on to)  then trim it right up to the edge with a sharp scalpel blade, then mylar over the top. I havent tried waterslide decal on a spinner yet but i may give it a try on one of my future restores.

I checked out the Avery website, and along with the white labels Nino referred to above (J8167), they also have clear labels (J8567). http://www.averyproducts.com.au/avery/en_au/Products/Labels/Shipping-Labels/Clear-Shipping-Labels-J8567-25-Pack-199.6-x-289.1-mm_936008.htm.

I suppose the advantage of using the clear label (compared to the white label) is that you would not need to match the colour of the "background" of the printed spinner art to the rest (ie. painted) area of the spinner (its edges).  As Buccaneer's artwork background is white, this is pretty straightforward to match and using a white label (eg. the J8167) is fine.