Which method of gold trading is the most secured one?

[Karano]

I currently have a mule account which has been "testing the water" with several gold vendors. I've been taking some pre-cautions: buy in small amounts, mail in small amounts, and level the mule toons past level 1 and below level 10.

So far I have seen three methods of delivery: AH, Mail and face-to-face. It was my understanding that AH delivery would be the safest, and it seems to be the method most vendors offer. However after reading a bit more it seems mail, and especially face-to-face are in fact more secure? Wouldn't conspiring with a level 1 with random name appear more suspicious? Why is face-to-face the most secure way of gold trading?

The second question then is how to transfer my gold from the mule to my main account. In the past what I've done is to post a vanity item which actually worth quite a bit (e.g. rare whelplings) on AH with my main account, then buyout with my mule account after half a day or more. After awhile I would then send the vanity item back to one of my main account's alt, sometimes as a small CoD. I lose some gold due to auction cut, but it seemed to be secure. Would it be much better off if I simply traded the gold from mule to main face-to-face?

I still only understand Blizz's gold-trading tracking methods more as myths than knowledge. Any tip would be greatly appreciated.

Side note: my mule and main accounts use different IP. I always use my main account through tunneling services, while the mule account would be used through default launcher.