A heat gun or paint stripper might be a better idea than using sand paper to remove the existing finish. Then follow up with a light sanding.
When you do this remember how much trouble it is and then compound that by a large multitude to imagine how hard it will be to remove a failed epoxy finish. What are you really trying to accomplish? If you are looking to reduce maintenance and change the appearance, tinted epoxy is not a great choice. Epoxy should still have a clear coat covering the surface to protect it from UV rays.
If you want a black paddle, why not simply get yourself a couple of spray cans and have at it? If you ever imagine you might want to take it back to a bright finish then give it a sealer coat of clear before painting. Paint is far easier to apply and maintain than epoxy would be. If you get bored with black you could do fades, color changes or designs whenever the mood may strike. Clear finished on wood do have the advantage of transparency to be able to spot flaws in the underlying wood. I doubt this is much of a concern with your paddle.
With paint you could retry or build the finish as often as you like. With epoxy it would be good to get it right the first time. If you don't already have some form of edge protection on your blade tips, this would be a good use of some sort of fiber and epoxy before you paint your paddle.
You could have lots of fun with this, Steve.
The Connyak BBS