The Sawyers spray seems to work well. For all over repellent the ones with Picardin seem more effective than DEET but bring both as one might work better for mosquitoes and another for flies & gnats. If no seeums are around then sealing up your sleeves helps or a double net jacket and pants like the Sea to Summit is really the best. These can be treated with Sawyers or the Picardin and the bugs don't even land on them. Ask your guide if it will be mosquitoes only or black flies and no seeums which are an even worse nuisance. If all three I would get the mesh gear including the head cover.

When I worked in Alaska I became immune to mosquitoes but never to the others.

"When you disarm the people, you commence to offend them and show that you distrust them either through cowardice or lack of confidence, and both of these opinions generate hatred." Niccolo Machiavelli