OK - that should be fine. Put some hooks in the ceiling, put a rod (broomstick) across the two hooks, and find the fluffiest comforter you have in the house and hang it over that broomstick.

PUt the mic about 18"-24" away from the comforter. Record your vox with no EQ. The SM58 is directional enough that you should be cool.

Experiment with two broomsticks 3-4' apart and hang that comforter across both of them, making a sort of booth.

SM58 is actually a really nice mic to use for home recording. But if you have big-time room issues, then you are going to have issues in the recording that are very difficult to remove after the fact. It's not just about EQ, it's also about early reflections that shouldn't be there - those cannot be removed with EQ.

I generally go for the sing quiet method. But I've got enough treatment options that I can belt it out if I want to as well and not get major room noise in my recordings.

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