I used elecrow's metal stencils a few times and with good results. They are better IMO than those oshstencil's plastic ones (which are very good for the price).
Assorted suggestions/notes
* The stencils they send me are large and my boards are small so I trim them with metal shears, leaving about 1-1.5" margin around the stencil holes.
* Hold the board in place with L shape brackets of the same height as the board (typically 1.6mm). I used oshstencil's brackets (
https://www.oshstencils.com/pricing.php ) and 3D printed ones (like these customizable brackets
http://www.thingiverse.com/thing:530949 )
* Place the board and the brackets on a flat surface and secure the brackets (not not the board) with sellotape. Make sure the bracket are secured such that the board cannot be moved.
* Place the stencil on the board, align the holes carefully and secure the stencil on one edge further from you using sellotape such that it acts as a hinge (so you can do multiple boards).
* Use a hard and straight tool as a squeegee. I use a 4" joint knife. Apply the paste along the edge of the squeegee and then pass it slowly *once* in one direction along the stencil while pressing it down. Hold the joint knife at 45degree toward you.
* Lift the stencil and remove the board by prying along its edge.
* If the paste was not printed well, wipe it clean with IPA, let it dry and repeat (don't print over existing paste).
* Clean the sqeegy and remove the extra paste to the container. I used paste in small jars and use paint knife #1 to manage the paste
* Clean the paste from the stencil, and squeage using IPA and soft paper (I use KimWipes).
http://www.ebay.com/itm/5-pcs-PALETTE-KNIFE-Stainless-Steel-Spatula-Painting-Mixing-Knives-Set-/311339947311?pt=LH_DefaultDomain_0&hash=item487d4e952fBTW, the elecrow stencils I got were made of (stainless?) steel, not aluminum.