I use a Radial Arn to cut all my scarfs. I made a jig out of 3/4 x 3/4 pine. You could also do this on a table saw. The jig is a triangle that clamps to the fence of the saw. It positions the strip so the radial arm cuts a 6 to one scarf on a strip that's held edge-wise. I clamp the strip on edge with pony clamps (squeeze clamps) so I'm not near the blade. the saw is really cutting at 90 degrees - it's normal cut, the triangle jig holds it at a slight angle and gives me a surface to clamp to. I can cut up to four scarfs at once with perfect accuarcy in seconds.

When I glue up the scarf, I position it over another scrap piece os strip (about 2 ft long) and clamp the ends. Then I seperate the scarf, add glue and put a squeeze clamp over the scarf. I use a little of wax paper to prevent the scarf from gluing itself on the scrap piece. with the two clamps on the ends , it prevents the scarf from sliding open and keeps the joint in alingment.