Bora-Care is the preferred choice to treat wood for any insect issues if most of the wood is exposed and it is raw wood you are treating, meaning it is not painted, stained, or sealed, it is just normal wood. If your wood is stained, then you would either have to sand off the finish to use Bora-Care, and then you can re-stain it after 24 hours of applying Bora-Care, or your other option is to drill holes every 6 inches apart into the center of the wood and inject Bora-Care to get it past the outside stain. Bora-Care is made only for wood, and you do not have to know exactly where the termites are for it to work which is a plus. Bora-Care is sprayed evenly over all exposed surfaces of the wood and actually penetrates through the entire piece of wood. When the termites in the wood try to consume the wood after it has been treated, they ingest the Bora-Care with the wood and die. No matter where they are in the wood the Bora-Care will find them as long as you treated the exposed wood that you can see. The other main benefit is that Bora-Care stays in the wood forever, so you will not have to worry about termites or beetles infesting the wood that you treated ever again. Also, Bora-Care dries clear so you can paint the wood, stain it, or leave it looking natural.
Bora-Care: http://www.domyownpestcontrol.com/boracare-p-100.html
You should drill whatever size hole you need based on what you have available to inject the Bora-care with. Typically if you have an injection piece of equipment, 1/4 inch or 1/8 inch holes are used. Please see this technical bulletin from the manufacturers of Bora-Care that explains about drilling and injecting into wood. See page 5 and it will give specifics about the drill pattern, etc.
Foaming would definitely be the best option for your scenario. You mix Bora-Care as you normally would at a 1:1 ratio (one gallon of bora-care with one gallon of water). After you mix it, pour the solution in the foamer and add Pro-Foam foaming solution. You want a high expansion foam so you should mix 7 to 10 oz. of Pro-Foam per gallon of bora-care solution that you make. Then close the lid, shake the foamer, and pump it like you would any other hand pump sprayer. The Chapin Poly Foamer comes with a coiled hose and ¼ inch tapered nozzle. You can get the Chapin poly foamer in a 1 gallon model or a 2 gallon model.
Here are links for you to see:
Two gallon poly foamer: http://www.domyownpestcontrol.com/chapin-poly-foamer-gallon-2659-p-292.html
One gallon poly foamer: http://www.domyownpestcontrol.com/chapin-poly-foamer-gallon-2658-p-495.html
Profoam foaming agent: www.domyownpestcontrol.com/profoam-foaming-concentrate-p-307.html
Hope this helps. Please let me know if you have any further questions.