RAW Double Exposure

I used the technique of double-exposing in RAW one of the photos I'd taken of Pevensey beach to get both sky, land and sea looking their best; then merging them in Photoshop.  It worked well, making the final image far more attractive.  I first came across this technique in one of Scott Kelby's books.  I feel that the ideal way to edit photos is to do so as a whole, without the use of masks, which is the way Dan Margulis generally does it.  But in practice I admit to using masks quite a bit to get the results I'm looking for, lacking his exceptional skills.