Macro work on the 'Old School' 100-300mm L

I know the old 100-300mm L is not a 'true' Macro lens. But I'm curious if there's anyone that has experience using the 'macro' features of this lens.

Essentially, I'm trying to kill two birds with one stone....
(1) I want something that can hand 200-300mm range....until I can afford a 100-400mm lens.
(2) I want something that can give me some macro opportunities as a macro newbie.

I've read how this lens does for (1) but I can't find anything on how the 'micros' works or performs in the field.

I know it's no 60mm or 100mm macro lens, but right now I'm not ready to pump that kind of money into a dedicated macro lens....at least, not until I know I really want to shoot more macro. And right now, it's something that I really only want to dabble in on the side.

Would an extension tube set be a better idea for a 'macro' newbie?

The 100-300 provides 1:4 macro so it won't get you very close, a 50mm with the Kenko extension tube set would get you around 1.36:1 so you can get a lot closer with extension tubes. The 100-300 should be fine for getting some decent results of larger things, though extension tubes with a 50mm would get you a lot closer.

I would get the extension tube set, these can still be used with a macro lens if you purchase one later on, with the 100mm the set would give around 2:1 magnification.