Those PSA blanket auction lot letters don't mean much; they apparently just skim through the stuff. The Bill Daniels lawsuit (scandal largely ignored by the hobby press) shed light on this practice a couple years back. They're far better than, oh, STAT or Morales, but that ain't saying much...
As far as Andrews goes, I don't know his signature and can't offer any advice...wish PSA would do the same instead of making like they have total knowledge of all signatures in all fields throughout the history of the universe. David's 'the man' as far as Yankee stuff goes, I'd listen to him over them any ole day.
Apologies for the rant, but I can't resist sometimes...