The BSP only has one MIDI out port, so what I do is (for ease of use) I bought an external MIDI thru box, connect the BSP to the MIDI In port of the box and use the MIDI Out ports to connect to my different synths. For your setup you'd make do with a simple four-port box such as
this.
Alternatively, since both your synths have MIDI Thru ports, just daisychain them one after another, like so (for example):
BSP MIDI Out -> Airbase MIDI In -> Airbase MIDI Thru -> Juno MIDI In.
Then just configure different MIDI channels to the synths, match them in the BSP sequencers and away you go.
