Leading is an issue everyone talks about but is never an problem with a high quality cast bullet. If you only shoot a good cast bullet, don't worry about it. If you shoot a combination of cast and jacketed, scrub the barrel before you run any jacketed through it. But, even if you forget, it's typically not a problem. You just end up cleaning the barrel without the elbow grease.
I have at least 10k through my shadow and have never cleaned the barrel. I scrub the chamber to ensure consistent feeding...no more. Yes, it's polygonal rifling. Yes, they smoke. If there's a breath of wind you'll never notice. No, I have never seen a decrease in accuracy due to not cleaning the barrel.
I have videos posted here: YouTube.com/kalebg35 and even in a hot, humid climate like Arkansas, smoke was not a problem except for two targets on "the door" stage.
Practice or matches, I only shoot cast bullets and I get them here: shooterready.biz
Hope this helps.