Stouts: Looking for ones that finish clean

Also I do remember having an oatmeal stout called buffalo sweat by tallgrass brewing. That seemed pretty similar to Guinness but with just a bit more body/ flavor

 

Why am I thinking of Smuttynose robust porter right now? It is nice and hoppy and have none of the dirty flavoours you dislike.
Also, Goose Island Night stalker but that might be harder to get.

To be really frank, the brittish make better low alcohol porters/stouts that is much drier than the americans. I tend to prefer the american styles more, but the brittish are often a bit more clean.
With that said, check out any porter/stout from an older brittish brewery and you might find what you are looking for.

 

Murphy's IMO is better than Guinness and you can still enjoy the nitro can. Brooklyn makes a fine Dry Irish Stout as well.

 

Left Hand Milk Stout nitro is really worth giving a try, as well. If you don't really like it (like I do), I would be shocked if you disliked it. Flavorful but easy going, if that makes any sense. Plus, it's affordable and easily accessible.