I can't wait to try the baby oil and dettol. I have been eaten alive since we ran out of 100% deet and have been searching for it everywhere (despite seeing it in action melting plasic, the bites are just getting to be too much), hopefully I will have some luck with this new mix. I have tried Off and Autan, Off cream has been the better of the 2, but still not so flash. For itchy bites, try using some vicks vaporub, it kind of gives it a nice burning sensation (better than the itching!) and also cools you down a bit.
I think the main problem with a lot of bug repellents is that you sweat it off in a short amount of time. Long tops haven't even worked so well as the hungry mossies in Palenque managed to bite thru them - we had to wear 2 layers, boy that was hot! I have read in some travel guides that treating your clothes and mosquito nets with permethrin is good, however I never found permethrin in the States before we left on our journey or in Mexico - is it a mythical substance??