The most efficient way to do the moonshiner role is :
1. Do a story mission - choose the 3rd one on the boat. This mission is easy, takes about 12 to 15 mins and gives about 1,5k xp
2. Do a moonshiner mission and get back to moonshine shack.
This action will reduce the mash cost to 10 RDO$ and deliver 2k xp.
3. Set up the moonshine - i only choose special moonshine when there is a daily mission for it. IMO its not worth to sacrifice a colectible for 20 rdo$ more on the shine. Its better to keep the colectible and deliver the sets to Madame Nazar. If you want to make the best mash everytime tho - choose the one with carribean rum - its the most common to find.
4. When delivering the mash use auto drive as u mentioned but controll the speed especially on bridge enterance or exit. For me slow trot works the best. Keep in mind that the wagon also auto drives when you press and hold aim. This way you can drive and shoot the agents without problems.
After you deliver without breaking you get about 937 xp for the delivery of 2* shine.
5. Repeat the process.
Overall moneywise its close to Trader but exp wise better than trader.