Another GSD

Hi all,
       As you can see above there is another GSD on my drawing board, and this one is quite a challenge because he is mostly black, and the photo I am using is not the greatest in the world. His name is Jake and he has crossed the Rainbow Bridge, but as you can see one of his ears never came up, which to me adds all the more to his personality.There is still quite a bit to do but I am aiming to get this finished by the early part of next week and then it is back to the Cairn Terriers. Graphite size 12 x 10 inches.
     For most of you who follow this blog you will know that I love to create Mandalas and experiment  with different surfaces, and for a long time have wanted to try doing these on wooden rounds. I do have in my airing cupboard a round from a tree which has been drying out and I thought I might try something with this, but really a much smoother surface and better shape is more desirable. Surfing the net I have come across a couple of suppliers that provide these in various sizes, and whats more not just circles all kinds of cut out shapes as in butterflies,animals,angels,dog bones,ovals,square blocks etc, all ready to be customized. Having said that and getting all excited I do have a dilemma as to whether I need to size the shapes first or not and by that I mean apply a coat of Gesso before applying the paint ? As I intend to create the mandalas using Acrylic (metallic,glitter,matte,pearlescent paint,mixed media) and from what I gather on reading the info on site these are made from Birch. Some of the designs would be just fairly simple and I don't think Gesso would be needed but if I was to do something where the whole round was covered perhaps then I would need to add a layer first? For those of you who do work in Acrylic paint perhaps you could give me some advise...here is the link to one of the sites that I found
Wooden Shapes.
 As always any advice is much appreciated and thanks to a few new followers that I have picked up recently, not far off 200 now and I think I may have to find a way to celebrate that...perhaps a give away!