How Do You Use External Filters With Synths

Use of external filters with synths depends on the capabilities of the filter, but let's take Moog MF 101 as example. There are three possibilities; either you use a fixed cut off for constant pitch timbres like drums, or use expression pedal for cut off to increase cut off with increasing pitch keys, or send CV to MF 101 from the keyboard that produces the pitch information being played. I never tried it, because I don't know what CV a synth sends when playing chords for example. The problem is that envelope follower of the MF 101 follows the amplifier envelope of the synth, like a Juno 60 sharing the same envelope for both amplification and cut off. Key following of the filter is the issue here. Another thing I would like to ask is have you tried, for example, 4 MF 101 filters for 4 separate outputs of a particular synth, lets say an A6 for example. Filtering each output independently and simultaneously in real time with subtle filter setting changes would produce something like a blend of Oberheim Ob-X and MemoryMoog. What da ya think ? Also, is MF 101 a ladder filter clone, any info on this?