Marcel wave, tighter and stiffer; finger wave looser softer. The one can often relax into the other.
You really need the right tools and the right person, soemone who knows hot to do it. Then you have to sit for hours. And in order to keep it for the length of an event, sleeping with your head wrapped in a silk scarf very still is the only way. Honestly, I don't know how those ladies in the past did it every day!
So, I have a young lady who kindly does my waves for me, but here is a look at the process. And here is someone else's blog describing basically what happens. The important thing about finger waves is to get the correct clips. My girl likes the vintage banana ones, sort of like those big plastic ones from the 80s only smaller. They yield a very tight wave, more like a Marcel then a finger.
Bellow you can see that the top part is finger waved while the bottom is pin curled. It's impossible for me to sleep in the wave clips, but I can sleep on the curl clips.
And the final look, slightly brushed out.
These days my hair is shorter, and I'm less stressed about getting it perfect, and I sleep on it without as much care to fly always, frankly I don't have much time. But, there it is.
Here is a youtube version for longer hair using more modern clips it results in a looser look, like this:
And here's a post on my favorite hair style ever, a 1940s look for the Hugo Awards in 2010 done by the amazing Kat in Melbourne, Aus.
Retro Rack is also on facebook where I post additional images and fashion thoughts.