Yeah on the video that pixelgrotte posted, at 4:55 ahmed explains it pretty well, if you get used to it, it becomes like muscular memory and you'll do it without really thinking.
And if you're just using the regular brush(in photoshop), and not the mixer brush there's no way it's smudging, soft brushes do make it easier to blend but you can actually do it with a harder brush and have a bit more control so maybe try with a 50% hard brush.
And then there's the thing about complementary colors, it means the ones that are opposite on the color wheel,(ahmed actually uploaded a video on that recently, I haven't watched it but I guess he'll explain it in there).
So yeah the point is this:
So just be careful about not mixing those too much, sorry for my english I hope it helps