It can be done.
Bear in mind that my swinging arm was off at the time, this makes things a lot easier, and not a bad idea to check the bearings anyway...and re-paint the arm too come to think of it.
The alternator side comes off so easily it's not worth masking it up in place.
You might notice that I took all the cover screws out to spray. I managed to leave it like that and not break the seal. I replaced with new polished screws after spraying (with VHT).
You could just spray the screws and replace them one by one afterwards I suppose?