or use the import alpha mask plugin
sometimes i have my own ways to cutout something for example (duplicate layer) i run the pencilsketch effect and then erase the things i want to select, after that you can click with the magic wand into the erased parts and voilá.
Or make a new layer, change the opacity to around 120, then draw with red or any other color your selection, after that click with the magic wand on your drawed parts, then back to the original layer and delete the "draw layer".
edit: in your pic Technokitty i would only click on the white with the magic wand with a tolerance from ~16% then press delete.