I can attest that building themes are a royal PITA due to the reasons Bil outline in his post Site Settings, Apply Theme, Apply, Lather, Rinse, Repeat.
Bil has taken it a step further and provided an idea for a simple web part that makes this process go a little easier. Check it out.
Now all we need is for Bil to provide this little ditty for us complete web part morons so we don’t have to build it. Hint, hint, nudge, nudge, say no more.