Questin about drug test using synthetic urine

So i've been reading that the best way to pass a drug test is to use the synthetic urine. I have done this before and failed because the temp. was to high. I used the warmer and it obviously worked too good! Has anyone had this problem before and whats the best way to get it to the right temp? Also has anyone had to take a test where they were in the room with you? Any advice will help! Thanks

I put it right at my belt line (against my skin) and that will put it at body temp and obviously use a belt and nice shirt over your belt and there yah go works for me everytime lol you feel so James Bond after it