You're not the only one who finds seperating commonly-named feat. artists tricky!
Trying to find the same release in another database, eg rateyourmusic/ discogs, is a easy way of identifying the featured artist, and finding out who to match it to/whether to create a new one, if you're lucky.
If that fails, giving the actual song a google and seeing if it pops up on an existing artists website can help to match it.
Personally if after all that I'm still not sure I would create a new artist, with the disambiguation either (unknown), or (featured on X track with X artist). You don't have to get it right if you don't have time!
If I do spend the time doing the research to figure out who the exact artist is, I often find out a bit about the other same-named artist in MB while I'm at it, and usually spend a while sorting those out as well, seperating and disambiguating them.
It really depends what you want to do though - if you just want to do the easy ones then that's helpful as well, there's no pressure to do everything!