Using cleaning slime is tricky. You need to knead a piece into a firm ball, then dab whatever you are trying to clean. Do not let the slime sit on any piece of electronics for more than a second because it will start to ooze inside of the unit and will potentially ruin it.
After trying my homemade slime, it just seems like a lot of work when you can just whip out a cleaning cloth. It does pick up dust and lint from nooks and crannies, but it can leave behind a residue if the mixture hasn't been kneaded enough. It was really fun to play with while I cleaned though, so it's worth giving it a try.