Ron,
The quick way is to free hand the countersink. Use a scrap and practice, the bits can grab with little pressure so get a feel for it. A sharp bit requires very little pressure. Use a very low speed on fiberglass.
I often free hand in aluminum as well if only needing to do one or two holes.
A ready extension for threaded bits is a cable turnbuckle center. The clockwise end is a match to the bit threads, also drill bits. If you have the equipment lathe the unused end for easier chucking to a drill.
Good luck!