Smocking the top of a panel is really easy, whether you are using pencil pleat tape or simply using standard header tape.
I use pencil pleat tape when I only want 4" of smocking at the top of my panels. My preference is an Austrian tape I found years ago at a show:
This tape is "Velcro Ready" meaning that there is loop woven into the back of the tape so that you can simply attach your panel to hook that you have stapled to a board. After you have sewn the tape to the top of your panel, pull cords, even up the spacing & smock using buttons or beads.
If you need more than 4" of smocking at the top of your panel, remember proportions, proportions, proportions, you may either prepare the top of your panel as if you were going to stitch standard pleats with buckram or if your fabric is stiff enough, buckram isn't necessary.
This picture shows how I measure for spacing across the top: 3" at leading edge, then 1-1/2" in the little pencil pleat, then 1" spaces. But of course, I adjust this spacing for how heaving the fabric is, how long the drapery is (if the panel is 24' long & viewed only from the bottom, then I might put 3" in each pencil pleat & make the length of the pleats 12 to 18" deep (long). Test drive your proportions before making the actual panels.
These pencil pleats were stitched with black thread so that you could see them on the photo. Then smocked with black also. This would be great with beads or little buttons over the stitching.
This picture is taken on my table the way I work on it, opposite of how it hangs. The black really looks terrible.....but you get the idea.