The "dead cat/kitten" things are really effective against wind noise outside, and I've only used them on digital recorders and a shotgun mic, i.e., things that are some distance from the source, and not really trying to manage plosives. I suppose they'd help, but I wouldn't ever use one on a stage vocal mic.
The foam is decent for plosives on stage mics and also helps against wind noise, but you have to toss those in the washer (in a mesh bag) periodically. And I kind of shudder when I see them on stage mics at performances where one after another folks get up to use them and proceed to put their lips right on them. (But, I don't know anyone that got ill from one either.) These days, unless it's outdoors and wind is a problem, I'd skip them and just wipe down the SM58's built-in metal screen periodically, and deal with the internal foam between shows.
