I've really gotten into this "wet on wet" texture technique after watching this youtube video by Misty Russell:
Wet on Wet Texture Technique:
1. Lay down a thin layer of gesso. You can let this dry or move right into adding texture.
2. Use molding paste or more gesso to add texture.
a. Draw or scrape into a thin layer of paste (or gesso).
b. Lay down paste or gesso through a stencil.
c. Stick found objects or paper into the paste.
3. While the paste is still wet, begin adding paint.
a. Drip watercolors or water-downed acrylic paint.
b. Spray or drip alcohol inks
c. Drip Indian ink (spread with a spray bottle)
Once the page has dried you can dry brush paint over the top or rub pastels into the texture (as shown above).