Oooh OOooh - I can help you on this one.
Here is what you do.
Paint the platform the base color that you want. You can do one coat if you want even if you don't have full coverage as long as the area that you are going to tape over has full coverage.
Then tape out the design/pattern that you want.
Next, with the tape still in place, add one more coat of your base color.
Finally, still leaving the tape in place, paint over with your final/next color going over the tape and all.
Now you can remove your tape and have super crisp lines.
What happens is, any bleed through you get will be with the base color and not show. That bleed through also clogs any areas to prevent any future bleed through with the next color.
Hope this helps. It's a little secret I've been using for years for painting guitars and even my cornhole platforms.
If you do get any bleed through it will be very minimal and easily touched up. I usually use a small paint brush. If using a spray paint I just spray the paint on a paper plate and then use the brush to brush it on more acurately. Although, with this method you shouldn't have any bleed through.
