Was a couple years back I ran into a similar situation with- a Yella' dog, kinda' ironic
He bit me.
First things first, someone mentioned that some pros wash out aggressive dogs- keep this in mind it was a good post.
Also see post #10.
Didn't have to go to the Toe Hitch but it is an option. Found a couple things that were of my own errors- I was moving entirely too fast for the dog I was working with , so keep that in mind as something to consider.
Secondly-
Thot it might be a good idea to establish to the dog just exactly whos' the Alpha 'round here, (and who you can have some fun with too), since the dog had absolutely no leadership for quite some time prior to training.
3rd-
There's no big rush, so take your time. Each dog is different on the ears, so the amount of pressure you exihibit on one that changes behavior, doesn't mean that
sameamount of pressure will be applicable for the next dog.
Having control over the dogs' head is a MUST, no matter how you go about achieving it, and NO matter if the dog doesn't appear to be aggressive at the moment ,don't worry- as soon as there's pressure it changes.
Guess by now, your buddys' dog knows what's coming, so more than likely when you put your hand up there he clicks in the "mode".
Use a wide flat collar so you'll have better control over the dogs' head, along with a possible overhead rig.
Don't cave in to the aggressiveness, and don't cave in to a Hollywood actress. However in terms of aggressiveness, would say one needs to know when it simply isn't do-able.
Helps if the dog knows that FETCH means open your mouth and take an object before you even get on the table.