JanRN's the pro as she's done the SAS via PPing so recently.
When I've been doing the FWS/PC blocks, I leave the paper on as I join the seams. To get the matches, I stab pins thru the seam line to the opposite piece where they should match. Leave them stabbed in there, and standing straight, and pin between the normal way. Then pull out the straight stabbed ones (clear as mud?).
Then stitch on the line. Press seam open. I leave all the paper on, excep the outer 1/4" of the seam, which I remove as it will get buried with subsequent seams. Like JanRN, I leave all the papers on til the end, as it keeps my 1/4" seam liines marked all the way thru to the finish.
Press after every seam. Then a good pressing at the end. And finally, remove the papers!
