I'll say the best way to do it is using a stencil, which you can create your self. You can get stencil paper at a craft store and cut the shape or just do it directly on the wall with painters tape. Draw the lines on the wall first with a pencil using a level so it's straight. Buy stencil brushes or with a sponge, apply the paint by tapping not brushing so the paint doesn't run behind the paper or tape. If you use tape, be sure to take it off as soon as you finish painting to avoid pulling dry paint. If the paint runs a little, have a wet cloth handy to wipe it off as soon as possible. When you finish making the frame shape, do the shadow. When completely dry (Better after 24 hrs.) Mask the painted shape with the tape, leave a space along side the frame line, and forming the shade shape, put tape at the other side ( forming the shade). That would be at the bottom side and the right side of the frame stripe. At the corners the shade will conect to the frame on a 45 angle. You can use acrylic paints and thin them with glaze. This will give you more time, before it dries, to get the finish you desire. To paint this frames would take very little paint.