Watch the C7 F9: Pt 3 online guitar lesson by Brad Carlton from Guitar Lab: I7 to IV7 Vamps

Example 25 demonstrates a principle when dealing with this C7 F9 move. Notice that the top two voices of the C7 chord form a C5 and the lower two voices are the guide tones. All you have to do to move to the F9 is lower the guide tones one half step.