If you would like to be really safe, go to the duel arena and stake it to your mule. Even chat up between the two accounts make it seem legit as possible.
If your main and mule share the same Ip it doesnt matter how you transfer since both accs are linked.
If you have main on 1 IP and mule on a different IP you can stake it but there is a fee or you can drop trade , kill one acc with the other , etc.
It depends on the amount of wealth being traded to cause red flags. You can have your mule die to a monster and have your main pick up the remnants. The duel arena would be pretty obvious especially given the disparity in levels.