John,
Hahnemuhle states that their canvas doesn't need spraying after it's printed on to wrap, but it's recommended to coat it for safety. Any matte finish spray will be good to coat; otherwise you can use a matte liquid finish (Premier Eco or Clearshield) that you roll to keep the finish it already has. There is a chance that it may dull the image out a little, so I would stick with the spray if you don't want that to happen.
With canvas, it's usually recommended to apply the liquid version to help cover inbetween the weave better than spray- but it's user preference.
If you want, you can check with Hahnemuhle directly for their advice: 815-502-5880
Hope this helps
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