Hi LG,

According to the Shettles Method- missionary position favours a girl- but I personally don't think that matters too much.
I haven't heard of the vinegar tampon- that's probably going a bit too far for my liking!
I think the timing factor is the most convincing of all the methods (pre-ovulation for girl). Having said that, it seems that many women have DDT in their peak CM phase in order to conceive a boy, and have still ended up with a girl, so its certainly not foolproof. Maybe you could try DTD deed the night before the day you ovulate so its not too far away from your peak fertile period?
I know that doing a detox (both male & female) leading up to TTC significantly increases the chances of having one stick- but that goes for both male and female sperm. The Quick Cleanse 15 day one from the chemist/health store helped friends of mine to conceive after long term TTC.
Can't offer much more advice I'm afraid. I've read heaps of info on TTC a girl too and I'm not convinced by a lot of it. My diet has always been very low in red-meat and salt and my first bub is a boy (although I didn't do any gender swaying techniques for my first and did DTD at EWCM time).

Goodluck with your attempts!! Hopefully your DH will be more open to the gender swaying methods than mine!!