You should buy a newer formula icaridin 20% or 25%, no deet based solution. Buy something cheap from local drugstore which can keep you safe for the distance from airport to a drugstore in brazil. There you can buy Exposis Extreme with 25% Icaridin.
You need also a sun cream to apply underneath, go for Riemann P20 variants which last about 8 to 10 hours and uses the larger UV filters and healthier. You can combine this easily with the solution before, if you wait 20 minutes after applying the P20. Icaridin unlike deet doesn't impact the efficiency of your sun cream.
Vaccines: You shouldn't vaccinate for Dengue fever if you are travelling in the next 4 months. You will not have the time for a second shot and it would make you more vulnerable as the second infection with dengue is the more serious one. Vaccination would be your first infection. Yellow fever, Hepatitis A and Chikungunya are fine and you can do them.