What's the best way to curl long straight hair with a curling iron and keep round ringlets?

Is there a styling product or technique that will help keep the curls? It's okay if the curls are really stiff, just as long at they stay.

What's the best way to curl long straight hair with a curling iron and keep round ringlets?

I take an inch of my hair and spray it with a volumizing hairspray then curl it and it holds. but the key is to do small pieces of hair. Iknow it takes a while but it works and it will hold!!