I'm a fan of smooth sauces myself. I start all my sauces with seeds in them, use an immersion blender to smooth it out as much as possible, and push the sauce through a metal sieve with a spatula to pull out the bigger bits. I've tried food mills, but they either let too many seeds or not enough pulp through. I also wrap the left over seeds and pulp from the sieve with cheese cloth and squeeze out as much liquid as possible back into the sauce.
I also like
running the leftover seeds and pulp through a dehydrator and grind for powders. These make really wonderful complex powders