The modification of peptidyl-cysteine to form peptidyl-S-farnesyl-L-cysteine; formation of S-farnesycysteine may be coupled with subsequent cleavage of a carboxy-terminal tripeptide for the CXXX motif and methyl esterification of the farnesylated cysteine; the residue may be found at the first position in the sequence motif C-X-X-(SAQCMT)* where the second and third positions are usually aliphatic.