Hi!
I do mostly buttercream cakes. I use an American buttercream (shortening based). I use a scraper on the sides of my cakes and level the tops with a tapered spatula at eye level. Instead of putting one big glob of icing on the top and then smoothing out, I pipe my icing with an icing tip to get everything level. I finish the smoothing with a viva towel if need be otherwise I just use a bench scraper. No matter how straight I keep my bench scraper on the sides or how gentle I press with the viva towel, I seem to get these raised lip edges on my buttercream cakes. It takes me about 25-30 mins EXTRA to smooth that lip out and I am not always succesful. I dont get that lip all the time, just sometimes. I'm not sure what I am doing wrong or if there is any way to prevent this. I've attached some pics. One shows the lip and the other is once it has been painstakingly smoothed out. Any help is appreciated. Thanks!
Fedra

Maybe a different smoothing sequence might help.

You would ice the sides and smooth them with whatever tool you like. Then you ice the top and smooth that with the longest straightedge/spatula you can find. Ideally the tool should be longer than your cake diameter.

You don't have enough icing in the middle on the top to pull a straight edge right across the top in one motion.

You're being entirely too hard on yourself and spending way too much time on this. For what? I can't see a lip or tell a difference between either photo... they're both nearly perfect. Instead of playing with the icing for an additional 30 minutes, give yourself a break and stop because the extra time spent doesn't show, so why bother? Get it? How much closer to perfect does it really need to be?

This might help to speed up the process... slap the icing on the top and spread it out a bit with an icing spatula without lifting the knife. (A 10 1/2" knife with a 6 1/2" blade works well for this.) Give your turntable a spin with the knife blade extending near the center of the cake. The extra icing will be pushed to the edge of the cake and overhang. Scoop more icing onto your knife and use this, along with the overhanging icing, to push the icing around the sides of the cake. Scrape your knife clean. Now, use the edge of your knife at a 45 degree angle to the edge of the cake's surface to knock off the entire rim. (It's alright if you scrape a little too much off and can see cake at this point.) Next, spin the turntable again while scraping the sides smooth one last time. The extra icing will come up to meet the cake's surface while filling the rim that was previously knocked off. No more extra icing to deal with!

I agree totally with Unlimited and that's what I do with my cakes.