Very much enjoying your project thread, eagerly following along to learn, and one day build my own MC parts.
I've built boats, mostly plywood with one strip built dingy also (too time consuming but purrty). The cheese grater part mentioned is below, and when sharp are great for smooth n'fast finishing of foam and bondo. Like below I have one in my kitchen now. High quality ones from a good tool store
run about $14 each and are far superior to big box store products.
Oh, and small foam rollers work a bit better for gel coat and primer than a brush.