Chris,
Paint masks can be difficult to apply, especially if they are large.
I suggest you start by laying the mask on the plane, attach the mask with a 3" strip of masking tape, along the top edge of the mask, the tape will act as a hinge and allow you to cut the mask in smaller, easier to work with segments, while still holding everything in alignment. Cut the mask into workable segments, I usually make them 2' long. Lift the segment, hinged at the top, and peel off the backing, this will expose the adhesive side of the mask. Apply a liberal amount of "application solution" with a spray bottle to both the adhesive side of the mask and the aluminum. The solution can be made by mixing 75% water, 25% isopropill alcohol and a few drops of dish detergent. This will allow you to make small adjustments to the position of the mask, or to remove it and reposition if necessary. If you do not use the solution the mask will stick as soon as it touches the surface and will be impossible to move without damaging it.
Once the mask is in position, use a plastic squeege and remove the trapped solution and air bubbles by working them to an outside edge. Now remove the
top application sheet, Then, using a plastic squeege, remove all the air bubbles and trapped applacation solution. Next tape over the joints between the segments and then remove that portion of the mask that will receive the paint, "Scotch Brite" the surface to be painted and proceed with painting.
Hope this helps,
Dick