IFR in A/C with Single Nav

I am a relatively new CFII looking for some advice. I am starting an instrument student in a 172 that is bare bones IFR. The plane has a single nav with glideslope, a VFR GPS installation, and no ADF or DME. I haven't flown the plane on an IFR flight yet, but it seems that the way to make it work is to just have fast fingers, and good SA. Any tips on how to navigate/teach in this airplane?

I've been looking over local approaches, flying them on paper. If, for instance, a VOR approach uses a cross radial from another facility to ID the FAF then what is the best way to proceed? My plan would be work hard to nail the approach course as early as possible, and have the cross-radial VOR in standby. Then I could flip the nav to the cross-radial, spin the OBS and see where I was, then flip back to the approach VOR/course.

Of course, knowing the distance to the cross-radial VOR could be helpful. Using the 60nm = 1nm per degree of deflection on the CDI could give ete to the fix.

Am I approaching this correctly? Any advice, tips, techniques would be greatly appreciated. Thanks!