well for the ESI, you'll need to find an auctioneer (usually behind the counter in most cities / forts) and look through to see what people are currently willing to bid for them (i think 80-85 ped is going rate, but I could be wrong!)
as far as the % goes on the paint, people are paying approximately 194% of the tt value of the paint (trade terminal value can be found by right-clicking on the paint and clicking the button in the bottom-left of the window that pops up). So, if the tt value was 1.00 PED (which it isn't, but let's pretend ), then you should be able to sell it for 1.94 PED.