Hello commanders 
At the beginning, it's all not easy. I started cargo missions, and always earned between 3k and slowly sometimes 13k...
After a while I thought, let's try something else. the Cargo missions have that icon with a cargo piece and an arrow designed on it... the new type of missions I was going to try, had 3 little cargo pieces as icon: a very tiny one, a big one, and one inbetween those, I'm sure you see which one I mean
So, no killing needed? No, just 'searching'. Searching? Where? How? Easy.... heading to the system, the claimed piece(s) are supposed to be. I came out of the jump just in front of the star as usual, and here it's where it starts.
When you fly in supercruise faster, you'll always loose a hell of time slowing down, approaching the appearing USS and drop out. Now, less time consuming is following:
btw, if you have a fuel scoop, start scooping, then drop your speed to lowest one (30Km/s) whilst scooping fuel, if no scooping (needed), just lower the speed, slow it down to max (30km/s).
As this time you're at LOW speed (supercruise, remember!), check out for USS popping (simpliest way to not oversee them, look at your navigation panel on left side. As soon as one comes to sight, it's already DROP-out-of-SUPERCRUISE time after locking the USS of course. So here, no timeloss at all, as you don't need to approach it and lower your speed etc....
Now, other anti-timeconsuming trick: do this a few times (search-find), even if you found what you were searching for. Why? Because new USS might drop again that part you were searching for, so you'll get it more than needed for mission clearance.
Now back to station, to give the cargo to the mission starter! Now you've cleared your mission and got some money for it, DO NOT SELL on black market the stuff you've found in add on. Why?? Because if now a new mission asks you to retrieve that part you've got already, it's very easy to : accept that new mission, and... give out the cargo immediately, as you already got it. Easy money
A glitch for me which is a bit unlogic, but as long as it works, why not

Hope you enjoied, and hope it was clear enough
If not, I might do a little video with how to operate 
At the beginning, it's all not easy. I started cargo missions, and always earned between 3k and slowly sometimes 13k...
After a while I thought, let's try something else. the Cargo missions have that icon with a cargo piece and an arrow designed on it... the new type of missions I was going to try, had 3 little cargo pieces as icon: a very tiny one, a big one, and one inbetween those, I'm sure you see which one I mean
So, no killing needed? No, just 'searching'. Searching? Where? How? Easy.... heading to the system, the claimed piece(s) are supposed to be. I came out of the jump just in front of the star as usual, and here it's where it starts.
When you fly in supercruise faster, you'll always loose a hell of time slowing down, approaching the appearing USS and drop out. Now, less time consuming is following:
btw, if you have a fuel scoop, start scooping, then drop your speed to lowest one (30Km/s) whilst scooping fuel, if no scooping (needed), just lower the speed, slow it down to max (30km/s).
As this time you're at LOW speed (supercruise, remember!), check out for USS popping (simpliest way to not oversee them, look at your navigation panel on left side. As soon as one comes to sight, it's already DROP-out-of-SUPERCRUISE time after locking the USS of course. So here, no timeloss at all, as you don't need to approach it and lower your speed etc....
Now, other anti-timeconsuming trick: do this a few times (search-find), even if you found what you were searching for. Why? Because new USS might drop again that part you were searching for, so you'll get it more than needed for mission clearance.
Now back to station, to give the cargo to the mission starter! Now you've cleared your mission and got some money for it, DO NOT SELL on black market the stuff you've found in add on. Why?? Because if now a new mission asks you to retrieve that part you've got already, it's very easy to : accept that new mission, and... give out the cargo immediately, as you already got it. Easy money
A glitch for me which is a bit unlogic, but as long as it works, why not
Hope you enjoied, and hope it was clear enough