I own some CE2's and regular atty's, the regular atty's I use to sample juice say a new flavor I just bought. They are easy to clean for the next flavor by blowing them out. The CE2's that I got I had to fill with a syringe it may just be the ones that I got but under the white cap there is a rubber right that you remove and there should be 2 small holes across from each other and I would suggest filling from both, the second one will take less juice than the first.