The sequence SPEEDE can encode BERLIN as follows:
Perform Ceasar shift on SPEEDE to obtain AXMMLM.
Convert the letters from a KRYPTOSABC alphabet to an ABC alphabet to get HYSSRS. (This is easy to do by just looking at the first two rows of the tableau: “A” from the second line is beneath “H” from the first line, etc.)
Use the tableau by looking up the plain-text letter in the ABC column to the left, move across to the key letter in the matrix, and then go up to the ABC row to get the cyper-text letter. (eg. B on the left and H in the matrix yields N on the top row)
This yields NYPVTT.
All these weird combinations of Ceasar shifts and alphabet mappings are probably a waste of time, but at least it is possible to get some encoding mechanisms that “sorta” look like they might work. This helps me believe that K4 may be crackable by mere mortals after all.