Here is a (confusing) method to encode CLOCK to MZFPK using the word GLOOM in a running key sequence.
First perform a Ceasar shift of -2 on GLOOM to get EJMMK.
Get the indices of EJMMK from a “reverse KRYPTOSABC” alphabet (Z=0, X=1…K=25):
EJMMK = (14, 9, 7, 7, 25)
Now use those indices to get the corresponding letters from a normal ABC alphabet:
(14, 9, 7, 7 ,25) = OJHHZ
encode as in K1/K2:
P) …CLOCK..
K) …OJHHZ..
to get:
C) …HANWZ..
Get the indices of HANWZ in a normal ABC alphabet:
HANWZ = (7, 0, 13, 22, 25)
and convert to a “reverse KRYPTOSABC” alphabet:
(7, 0, 13, 22, 25) = MZFPK