I've been fooling around in this area lately.
Been rebuilding an engine, and am nearly done. What I did when I loosend these, was use the cam sprocket spanner wrench that the former owner gave me to hold the cam while I pulled the other way with the wrench. The cam adjuster/spanner was about 14-18" long, so it gave pretty good leverage.
It's not the "official" spanner, but a home made thing that sorta works OK. I don't know how much the Alfa one is (believe IAP and Centerline, etc sell them for $25-30) but you might find some other tool that could help.
Or, even make your own from a couple of pieces of sheet steel, bent, attached together with a hinge, and with the right size pins brazed in. Though I'm glad the former owner did it, instead of me..
Make sure you tighten it down real well, and bend up the fresh new cam locktab you put in there before, when you're done...