Are there any areas of useable radar coverage in class G airspace?

ATC can't vector an IFR airplane in class G airspace (which is why we say "entering controlled airspace fly heading...). In a terminal radar environment, controllers can vector airplanes as low as the minimum vectoring altitude. To go below that, and then descend into class G airspace, an IFR aircraft has to be on some sort of approach.

The reason I ask the first question in this post is because for an IFR aircraft to go into a non-radar area, they are usually required by ATC to go onto a non-radar route (i.e. airways, which are class E airspace).

I think most of the class G areas between 1200' agl and 14500' msl are in areas of little or no radar coverage.

It's hard for ATC to separate IFR aircraft in a non-radar area on random (not on airways) routes because there are no reporting points, etc... to know where these airplanes are, so I'm not sure of a time when an aircraft would be in class G airspace, under IFR, not on an approach.

If anyone's got more information, hopefully with some sources, I would love to see it regarding IFR in class G airspace.