Having been a professional trombonist my whole life, I was versed in reading clefs as one of the many skills that had to be learned. I became fluent in treble, alto, tenor, treble down an 8va, Bb transposed, F-horn, E-horn, Eb horn (like bass clef up an 8va), D-horn (like a transposed alto clef), bass clef, and of course as a bass trombonist, 8va lower bass clef because I had to. This was not just intervalic sensitivity but actual familiarity with clefs as it pertains to a fixed pitch instrument. Even while getting proficient in Gregorian Chant notation, I just read the position on the staff in what ever clef it starts on. I bemoan the fact that clef reading has pretty much gone by the wayside as archaic and yesterday, with the great staff of treble and bass clefs reining supreme. Even in my pursuit of easy to read music for compline I've 'dumbed down' the notation for our singers. This does make for the one rehearsal quick step but looses some of the old world charm. Attached is a clef heavy little ditty for your once a year amusement.
jefe