Here's a simple example.Q2 is an emitter follower to provide a high input impedance.
Q3 provides voltage amplification.
Of course, the required circuit depends on what the actual problem
is that you are having. If the output voltage is too low, then some
sort of voltage amplifier is needed. (The emitter follower gives power
gain, but not voltage gain.)
If the problem is just that the input to your counter pulls down the
VFO, then a common emitter stage may be sufficient.
Of course, a common source stage
like the one shown here might
be even better.
Or this one.