I did my IMCr in something like 16 hours. What helped me was bashing out holds and approaches on MS Flight sim. One, it is much cheaper and secondly you can pause and check or reflect on what you are doing and hone your skills that way. You have to be careful not to take too many shortcuts while using it as it might mess up your routine, and in real life you have varying ATC instructions, a non-precise wind direction and bumpiness etc... But if you're pressed for time, and want to do it in the minimum, find a good flight sim package and an aircraft that is a replica of what you fly, and I reckon you will do OK.
I am also an 'average' pilot - I never was a natural Biggles, but the IMCr will improve your skills and competence, and give you additional confidence.