First... cut your foam to the desired shape. I'm doing ceiling beams so I set up the gate on my table saw to 7". You can use a jig saw, sabre saw, Skil saw, hand saw or what ever you have. Remember... real wood has saw marks.
After we've removed all our sanding dust and created a work surface. It's time to paint. On the right is our newly distressed beam. in the middle is our first and only base coat of flat "woodland" . I used Valspar products - paint code 2006-5A. On the left is our completed beam, coated with Valspar "Java" satin finish (shelf item in my store) and wiped with a paper towel while wet to create a multi-tone/textured look.
Here's a close-up of the end of my finished distressed beam. The per beam cost (2" x 7" x 8') is less than $7.00. That includes the little bit of paint it took for each piece, the sand paper, and having all the tools already. Next... find some decorative nails to cover up the few screws I'll need put these up as ceiling beams.