You mentioned that you're not happy with the opacity, do you want more or less opacity? if you want more, you can always use good old house paint for poster prints. Acrylic house paint that is (eg. Benjamin Moore, etc.) I go the hardware/paint store and ask them for their 'mistakes', meaning someone ordered custom color and they didn't end up buying it. A gallon of mistake paint is usually around 5 bucks. Granted, you might have to play around with the color a bit, but I've been able to get light tinted paints that can be mixed to any color. And for posters, house paint looks great for not much money. It can be a bit runny to work with at times, but just don't flood the screen with too much paint. As for less opacity, try a paint extender on house paint. It will make it go further, and reduce opacity. I use house paint for gig posters and also for fine art prints for galleries, and I've had great success with it. Hope this helps.