I personally have found the laziest method to farming cds and stickers. I'm not taking all of the credit for this, because I got the idea from some video I saw. Regardless, just use a small stage format, and make three blocks at the bottom horizontally. Then stack three more blocks on both the far left and right blocks. This will create a "U" shaped figure with one block's distance space in the middle, creating a hole. At the top of these walls, make two treadmills to where they empty into the hole. And lastly, make a ladder for another character to latch onto somewhere close to the map to keep it from zooming out (I did it to the left of the stage wall).
Once you have this created, start a Super Sudden Death match with two human players (obviously), but one of them must be Lucario. Once you do this, just have the other character latch onto the ladder so he is out of the way, and then have Lucario constantly charge up his neutral B move. From all of the other designs people tell me about, this is by far the one that requires the least amount of work, since you just have to tap the B button, then wait for one to drop.
Now, it is sometimes a little hard to see a CD drop, so I've been thinking of a way to fix it. I currently don't have three controllers to test it out, so maybe someone else can and give me some feedback. Make it a team match, with two on the same team. The odd player out will hang on the ladder from before, and Lucario will continue to charge up his neutral B (I find that making him face the left wall completely, then charging it will cover all of the space required). The third character should be a small one that would be in the hole with Lucario, simply picking up the items as they drop.
Sorry if its too long...but that's the basic description of my CD factory. I've made a few, but this one I'm happiest with by far.
