Citronella candles are very effective with keeping mosquitoes out of a small area and are easy to transport.
I treat all our clothing with permethrin that I mix up and spray on or dunk the clothes into and it lasts for 6-50 washings depending upon the strength. It is 100% effective and keeps the mosquitoes from landing on your clothing. That greatly reduces where we need to apply picaridin insect repellant to be fully protected.
At campsites the spots closest to a meadow or creek are going to have more mosquito traffic at night. We prefer to let other campers have these spots and figure that they are keeping the mosquitoes fed and happy.