How old is he? Assuming 8 weeks or older, probably the best and easiest to obtain is Advantix (available through a vet). Another similar product is Vectra 3D. Both contain permethrin at a level safe to dogs, but should do the trick on ticks. There are some over the counter products, but I have not seen that they work near as well, and if I ever see a reaction to these type of products, it is always the OTC ones. I am a veterinarian.
Be sure and apply it at least 3 days before you leave, giving it time to spread to all parts of the body. Even so, after a day in the woods, check his feet (between toes and pads), under his tail, and on his face and ears.
txhunter58
venor, ergo sum (I hunt, therefore I am)