Not sure that the buffers would help, but worth a try.
I think the reason you are going to get some signal is that the blend pot is 10k, so at most you are adding a 10k resistor in the signal path.
First thing that popped into my head, If you really want to kill the signal from one or the other, maybe expose T1 which will let you completely turn down the wet, and do a similar pot to ground for the dry signal, which would let you completely turn down the dry...and sum those together with an op amp. It means you have an extra control to fiddle with, but it would definitely let you control the mix all the way to silence from either side.
I think the reason you are going to get some signal is that the blend pot is 10k, so at most you are adding a 10k resistor in the signal path.
First thing that popped into my head, If you really want to kill the signal from one or the other, maybe expose T1 which will let you completely turn down the wet, and do a similar pot to ground for the dry signal, which would let you completely turn down the dry...and sum those together with an op amp. It means you have an extra control to fiddle with, but it would definitely let you control the mix all the way to silence from either side.