How do I remove this style of bottom bracket? I am attempting to remove and replace the bottom bracket from a cheapish 1970s American department store road bike. I've gotten the lockring off, and now the non-drive side looks like this:

[Whoops, I definitely took photos of the drive side by mistake. You can look at them if you want: head-on view of drive side, angled view of drive side.]

The situation on the non-drive side is similar, but the only photo I have right now is slightly less clear: 



That photo's from a few days ago and I have since gotten the lockring off the usual way. What's the tool or technique that will let me get the bottom bracket cup itself out? My shop doesn't have a bottom bracket tool with notches like this, nor have I seen one online. I tried a pin spanner to no avail. It's difficult to see in the photos, but the sides of the notches in the BB are somewhat sloped, so the pins don't get any "grab" and just slide right out when I start to turn them.

That's what I've tried so far. What am I missing, or what else can I try?
When I fixed up my old bike it had a typical BB with fixed and adjustable cups. I planned on replacing with a cartridge BB so I didn't want to get the special tools just for a removal operation. Though I did get the special toothed socket needed to install the new BB (a cheap version online since I'll only use it a few times). Using a slot screwdriver, or better, pin punch or cold chisel, and mallet/hammer, you should be able to get the cup turning. Make sure you're driving it in the correct direction. To remove non-drive side, drive it counter clockwise. To remove drive side, turn clockwise. A small amount of penetrating fluid can help too.

Edit:
Forgive my crude sketching abilities, hopefully this helps. As in the side view, hit the notch perpendicular, and as in the top view, keep the pin/punch as parallel as you can to the face of the cup. (in this sketch this is for removal of the non-drive side). Depending no how stuck it is, it might help if someone holds the bike upright with the brakes on.