Or.... find the proper key that your singer needs first, and then start building the song.

That is the very first thing I do when I'm working with a singer, including myself. Once the key is good, then you start working on the tracks for the song....and they're all in the proper key to start with. No transposing needed.

Here's an example from my studio... I wrote this song and sang it in the key I needed. I approached a young lady to ask her to sing it.... I had to change the key for her. So naturally the song tracks were different. At some point, I was advised by a Nashville song screener to get a better singer with more emotion in her voice to present the song in it's best light.... so I did. Well, surprise, surprise, she couldn't sing it in the same key as the first singer so I couldn't use any of the musical tracks....She needed it about half a step different... Seriously? but yes, she insisted so here are the results.

First singer: http://soundclick.com/share.cfm?id=12024993

Second singer: http://soundclick.com/share.cfm?id=12024980

Note that the song tracks are similar but there is a difference. At first we tend to want to stick with the first one because we have gotten to know it and "it's the way the song is supposed to sound"..... but I have changed my POV on that many years back. If you did it one time and it was good, if you do it a second time.... this time you can make it better. And I prefer the second singer's version of this song now.

I no longer get concerned over any particular cool track..... but I have learned that if I hear something cool..... export it of freeze it before doing anything else.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.