Theo, the people at my lab say the most important thing to do before a UA is to eat a good breakfast, high in protein. I use my 'random' days as a good excuse to have steak and eggs or some other meat and eggs, hashbrowns, etc. They say the food is what makes urine, not more water. You do want to be careful of a diluted sample as that is considered a positive, same with any unusual additives in your urine. You should be very good to go with 86 days especially after testing clean at day 77. In our state, pre-employment tests are also done not observed which will take away some stress. The home test strips also work well and are very cheap, less than a buck from Amazon. I just did the home test again last night and am still showing positive over 60 days clean.
The best to you in your new opportunities and your new freedom to pee clean. I'll bet you are dreaming good too. I just took a nap this afternoon, first in several weeks and had another dream where I toked. It was very real as I wondered if I would be called tomorrow in the dream but also knew it would not matter as the damn stuff stays with us for so long. I was very happy to wake up from that one!
Jim, the regular attendant at the lab also informed me the "random" thing is based on a monthly average which was comforting. I thought they were upping me to twice a week for the last couple weeks but basically we get x amount of tests a month. You can go almost the entire month with no tests, then get hit every day to catch up to the monthly average.