My strat was to ask in ooc if any newbie barbs would sell / bank for me and I'd camp ice giants all day. I'd give them a % cut or tell them to take what they need. Generally I was getting great results with this method.
Some gold to plat strats I wrote based around ice giant farming in everfrost.
https://wiki.project1999.com/Balers_...or_Plat_in_ooc
The people who I would trade gold for plat or have bank my gold, generally asked me if I had fine steel to sell.
I never stepped foot in halas and netted tens of thousands of plat.
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Another thing you can do is bag drop swapping.
0. Make a barbarian alt on the same account with the highest CHA possible.
1. place items you wish to sell in a bag
2. Log out in a Secluded safe spot and when the timer says 5 seconds till camp then drop the bag
3. wait a second at the character screen and log in on your barb alt.
4. Sell the items, return the bag via drop method
5. Have someone help you transfer the coin to your main then or at a later time
(you cant drop coin on P99)