How to record a singer/songwriter with two figure 8 microphones for good separation.

Figure 8 microphones are fantastic at rejecting signals on the off axis... the side/edge. Position the microphones so the null point (the side) is facing what you want the mic to ignore. You can see in the video the Coles 4038 front is facing the guitar and the edge is pointed at the singer's mouth. The U87 face is pointed at the singer's mouth while the edge is pointed at the guitar, effectively ignoring it.

Correct placement is crucial and a small move can make a big difference in isolation.

VOCAL - Neumann U87
GUITAR - Coles 4038
PREAMPS - Trident 80b
COMPRESSOR - Maletomp vari-mu