You could try it before you take a nap, but might be harder.

When you take a nap, usually you feel tired throughout the day (if you know the right point to nap), so REM might come faster, but it just depends from person to person. I try to nap in order to WILD sometimes, but I don't really pull it off well. I just rely on WBTB at night to try and WILD.

These links here might help, but they just show that it varies for each individual, and you're usually tired when you want to take a nap.

http://www.dreamviews.com/f11/rem-af...n-cycle-83788/

http://www.dreamviews.com/f79/afternoon-wilding-110016/

Hope this helps, (and don't necro post those links, just showing references)