I found a 58mm Canon 500D close-up lens in wife's old camera bag, so I put it on 75-300mm and tried it out. The result was full of operator errors.
First, it took me a while to figure out the rather narrow focusing distance range. Then, after figuring out the said range, I couldn't keep my hand steady enough or use high enough shutter speed to get any decent close-up pics. A nice stable tripod would've been nice, I think.
I may try it out on 85mm f/1.8 (another lens I have with 58mm filter size) as I may get a better result with a lighter lens.