I knew it! LoL. I'm sure it isn't the only way to achieve that effect but it is one of the more common ways to get that dramatic effect on the sky like that. Never the less the photos are great.
Another method is layering multiple exposure images with blending modes and adjusting curves for each of those layers + dodge/burn I cant emphasize how much I use dodge & burn. It's like my bread & butter.
Well tips I have are all random things like turning the front wheel so that it faces the camera, shoot with the sun to your back if possible. Also shooting 30-45 minutes before the sun starts to set is nice.
never thought of going that route. Might have to try that layering of multiple exposure images much like a HDR type thing.