I use a sharpie a lot just because of the convenience. In addition to trout dots, they make nice crappie marks.
As Seakarp suggested, I have also taken a sheet of plastic and punched holes in it to make quick stencils. Punch holes with just about anything (or lay on scrap wood and drill) and use a razor knife to flush cut the underside if the stencil gets slightly dented in around a hole.
I also sometimes use those round dot stickers from walmart found the office/school department to make dots. They are like masking tape. You get 500 stickers for a couple of bucks. I paint one color, let dry/heat set, then put the dot stickers down, paint a second color, peel the stickers off with an Xacto knife and you get a dot of the underneath first color. It's useful for making those dot-within-a-dot brown trout spots. Paint silver, put down dot stickers, paint dark metallic bronze or whatever trout back color you prefer, peel stickers to reveal a silver dot, then use a black sharpie to make a smaller black dot inside the silver dot.
I have a hole punch that makes a small star. I can use it to punch small stars out of masking take. I have used the little tape stars to make stars on a lure like the dot method above. I could have done the same by buying star stickers.