Once you get more comfortable with slap, you'll find that muted notes actually help you keep time better.
Also, I'm not sure if it's the same for anyone else, but I find it easier to pop if I'm just coming off a slap. I feel like I get a bit of "bounce" or momentum from doing the slap, and it helps me pop properly.
One of my favorite examples of good popping is in the song Come Original by 311. He actually hits very few open notes, but it sounds funky as hell because of all the mutes. Check it out!
