I´ve tried several ways.......

with some dogs just placing my hand palm side up flat and ask "dame la pata" which is "give the paw" they paw.......with some I had to "pat" the inside of the leg of the paw i wanted to be given and as they lifted it i grabbed it and said the vocal command..........

later on I could say "give me the paw" and they give then "give me the other" and they switched paws.......so cute......

perhaps Fenway doesn´t likes to be touched in the paws (some dogs just don´t like that) you can try the "patting the leg" and see if he lift it (this is in a gentle way and then you can give a treat afterards.......