When Eduard released the Bf109E Instrument they also released a mask to go along with it. Unfortunately the only way to purchase this mask is through Eduard's store and you have to be a member of the Bunny Fighter Club.
Now when it comes to masking a model you could take and make your own mask with one of the many medias available, or you can purchase a ready to use mask for that specific model and cut your masking time in about half. The mask for the Instrument panel helps in several difficult areas. One of the areas that the really comes in handy is for some of the raised details on the instrument panel that have to be painted. Another very helpful part of the mask is for molded on bolt heads. It makes painting these a breeze. You can follow the link above for a better idea of what is included or Eduard has a great article on building the instrument panel which includes a breakdown of the mask. The article can be found by following this link: