removing cup-and-cone bottom bracket without special tools
I recently inherited an old mixte frame and assorted parts. A "Made in France" Motobecane. It was neglected by its previous owner and many of the parts are seized (it took about 2 hours to remove the seat post yesterday). The bottom bracket either needs to be replaced or greased because it does not spin freely.
I got the crankset off after quite some effort (using a crank-removal tool). I got the lockring off the adjustable cup using a standard household wrench. I've removed adjustable cups before because they had wrench flats, but this is threaded all around. It does have holes around its surface, suggesting I need a spanner tool. But I don't have such a device and I prefer not to have to buy something I'd only use once.
Is there another way to remove this cup? Would a hammer/nail on the holes to create torque work (like removing the lockring on a freewheel)? Any suggestions before I damage the frame?