if trafigura agrees to sell say a barrel of WTI crude oil @ $56 3 months hence. How would they hedge it?
There is no need to hedge in this case. I assume they they are guaranteed to own the oil in this scenario, and they already have a future price locked in, so there's no risk to hedge.
Now, on the other hand, if they were going to sell oil in three months are market prices, then they would have price risk. To offset that risk, they could buy futures that expire in three month and then sell them on the day of expiry (to avoid physical delivery).
Oil producers are less inclined to hedge in a contango market, because there is a reasonable expectation for the future price to increase. However, that depends on the reason for the backwardation. If there is backwardation because of a short-term supply shortage, then the future price may be reasonable and hedging might be prudent.
But again, hedging is not about trying to profit on future misprices - it is about eliminating risk.