They were both on Roger's ship so maybe you can expect some quirk coming from that (also so that they both are setted with just that). If not Shanks has actually plenty of experience as a pirate and most likely helped ton of people for decades so that could be an easy solution (somebody repays the favor). There is also the man who carries the knowledge of Ohara (Saul) somewhere in Elbaf if I am not mistaken. Anyway Oda has plenty of legit excuses for him.
Buggy... There are some chances he will eventually go to Impel down to get Doffy and Weevil at the very least (so that he makes a shiki crew) and if that happens maybe there he will find "buried" somebody who can read them.
