Firmata Processing sysexCallback - how to call from Processing?

Firmata library for Processing - anybody knows is there a way to call sysexCallback from Processing sketch?
From Processing Firmata source I can see

private void queryCapabilities() {

so this means we need to send bytes F0 (START_SYSEX) and F7 (END_SYSEX) to Arduino and some bytes in between (command and payload).

But how to send these bytes to Arduino? I cannot use Processing.serial because the port is already occupied by

arduino = new Arduino(this, Arduino.list()[0], 57600);