I recently tried a little trick Brian Fellhoelter described here... keeping the stencil moist with plain water, and a light spritz of windex on the blade before laying the stencil down. It does indeed help the stencil lay flat, and helps prevent ghosting and fuzzy images. To be fair, the roughest surface I tried it on was hand-sanded at 600 grit... your mileage may vary if your surface is coarser.