Unlocking RSI Credit
"Melt" all the ships down into RSI account credit that you wish to sell off from your account (using the "Exchange for store credit" button in the My Hangar section).
Buy the least expensive ship possible using a Credit Card or PayPal transaction (to retain giftability). This is usually the $20 Aurora ES standalone ship, found here.
Use the ship upgrades tool to select a ship which closest matches the amount of credit you wish to trade plus $20 (accounting for the base ES). Proceed to the checkout and use credit to buy the CCU.
Go into the My Hangar section of your account and apply the CCU (step 3) to your Aurora. You should notice that the Aurora remains giftable even though the bulk of it's worth was added through credit. You can move $290 worth of credit per ship, which will have a melt value of $310.