Another vote for the permethrin spray. It's great against ticks and chiggers, too (treat all your outer clothing). Just watch your exposure to it when it's still wet. Spray the clothing outside, making sure the spray is downwind of you, and let it dry thoroughly. While the squirt bottle is more economical, I found it much harder to get an even spray with it. I ended up with an aerosol can instead to get an even coating with less spray used per treatment.
Remember that if you are wearing trail runners, your ankles will be vulnerable, since the mosquitoes will bite right through your socks. My first trip with trail runners instead of boots, I forgot, and my ankles itched for weeks. Spray the outside of your sock tops or wear shortie gaiters!
Note that permethrin is not effective against biting flies (read the label). Failing a suit of medieval armor, a wind shirt over your regular shirt or base layer offers the best protection against those nasties. If you don't want to use chemicals, the wind shirt over a light base layer is your best bet. Note that Buzz-Off and similar shirts are also chemically treated, I believe also with permethrin.
The stuff for dogs that contains permethrin (K9 Advantix) is one of those spot treatments (applied on the back between the shoulder blades) that travels through the skin, and is not approved for humans. Please don't spray your dog with permethrin anywhere he can reach to lick it off (which includes all the vulnerable areas of the dog). Please discuss with your vet first!
The "other" brand of permethrin spray is Repel Permanone.