All artificial lashes are produced by hand and that doesn't always happen in most sanitary conditions. Because of that, it's very important to clean artificial lashes before the procedure. You can either spray them with an antiseptic or clean them with a micro brush with some primer on it.
A lot of artists use lash holders to make their work more convenient – lengths are typically already marked on them. Palettes can be meant for either one or several curls and made from different materials.