Line art and text wrap . . . how to?

Hiya friends. I'm trying to wrap text around a line drawing. I scanned the line art as grayscale and used the Blatner/Fraser technique for getting good line art out of it. This is now sitting in a graphics frame in my InDesign document. I would like to wrap text around the actual drawing. So I select the object, open the text wrap dialogue box, select Wrap around object shape and Detect edges.

I don't actually understand the results I'm getting. There are two drawings, in fact. In the first instance, the text is affected by the drawing but it doesn't actually wrap: it seems to go all over the place. When I select the frame contents I see a couple of ghostly light blue shapes, which appear to be the "edges" that InDesign is "detecting", but they don't bear too much resemblance to the shape of the drawing, and I certainly do not know how they got there because I never made 'em.

Second line drawing is completely different. I can't get the text to go anywhere near the actual drawing, in fact the text won't go beyond the edge of the frame no matter what I do. The ghostly blobs that seem to be shaping text flow on the first drawing, well there's no sign of any such thing here.

It occured to me that a workaround might be to draw a clipping path in Photoshop, then choose Same as clipping instead of Detect edges in the Text wrap palette. Unfortunately, I've never used Photoshop as a drawing tool before, in fact I've never had occasion to "draw" anything on a computer (I'm not an artist), and a couple of attempts have ended in tears. (Blatner and Fraser seem to assume that everybody already knows how to use drawing tools; but I'm at sea here.) Any lessons available anywhere? What do I have to know in order to be able to "draw" a clipping path around my artwork?

Can anybody walk me through this, tell me the steps I need to follow to get this to work right? I've successfully wrapped text around a high-contrast grayscale images in the same document, but I seem unable to recreate the same conditions that allowed me to do that. Hell, I can't even get consistency with two images on the same page that I scanned and tweezed, using the exact same methods, half an hour apart.