DJ - You
painted those clouds?? Wow!
Jak - I have a small folder of sky photos which I've taken myself which I use whenever I want to add clouds to a sky. (Colorado has some GREAT skies!!

) I simply replace the entire sky in the original photo rather than try to "paint in" the clouds. It can be really tricky if there is a lot of fine detail (like leaves/branches) that the sky shows through, so sometimes I have to fade the new sky more than I'd like so that the fringing from the original photo isn't visible. Usually, if I'm replacing a plain, flat sky (and I don't want to change the tone of the photo too much), I just use a sky with high cirrus clouds. You can make clouds look more "wispy" if you enlarge the sky photo your using for the replacement - that also gives me more leeway as I move it around to make the placement of the clouds vs. blue sky blend in best with the original photo.
I've never tried painting clouds - I just save my photos with lots of sky (even if the photo itself is otherwise no good). The other day I even turned a dark cloudy sky into a blue sky with wispy clouds just by increasing the saturation so that the dark gray turned blue - I was amazed!! (I still have no idea what gave me the idea to even try it - I must have been desperate.)
Jeanie