Know what your components weigh before you assemble them:
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Cool, but a kitchen scale gets more use, and can weigh the complete board.
If you are going to hand shape and sand things (especially any wood cores or parts), these will be you best friends/worst enemies.
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Homemade sanding blocks, to suit the project. These are heavy, for a boat. Thinner plywood can bend to follow rail shapes, etc. The one with the foam flooring padding is good for shaping rounded edges. Spray on contact cement holds normal sandpaper to it, easy to peel off when you hit it with your heat gun a few seconds.
Other good friends, saw rasp and surform. Saw rasp is good on hardwoods and epoxy as well as soft stuff. I know, you might not be using any more wood, these work on foam too....
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Another important one, easy to overlook: skin barrier cream!
Trust me you don't want to wait until you get a chemical burn before you start using this stuff.
You will feel less foolish ordering it with your epoxy supplies than a month or so later, when your skin heals and you are ready to finish whatever you were doing when your gloves leaked or whatever.
Clean up :White vinegar + Isopropyl alcohol, go on and keep a gallon of each around.
...just what came to mind.
Oh yeah, maybe some beer, and a chair or stool to sit and think...