Guide pulled from Reddit: Flux farming for Vault Dwellers : fo76 (reddit.com)
Morgantown will provide more stabilizing agents (High Radiation Fluids, Glowing Mass, Hardened Mass) than almost anywhere else on the map. Also a good source of cobalt flux (make sure to get both the airport and the train yard)
Familiarize yourself with what plants & fungi you are looking for:





The actual farming. Remember that flux spoils (becomes inert). Farm your stabilizing agents first (they don’t spoil).
Nuke Morgantown. You probably want to do this in a group, unless you can one shot 6-10 Bloated Glowing Ones in rapid succession at a time. Teammates get loot from each others kills if they are in close proximity to each other when they happen, so loot will be plentiful.
Remember that you need one of each stabilizing agent per 10 raw flux to make one stable flux. I try to get 20-50 of each before moving to flux farming.
Don’t forget to gather the Cobalt Flux in Morgantown. You can get close to 200 with the right perks.
Nuke your desired flux location & harvest your flux.
Perks. Don’t forget that Green Thumb works on flux. Flux spoils like food (Good With Salt helps with this) It can take upwards of 45 minutes to completely scour a nuke zone for flux. Use Green Thumb, Good with Salt, and Thru Hiker to maximize your take away.
Processing. The only Perk that I’ve found to have Any effect on the making of Stable Flux is Super Duper. I highly recommend that you use it, in all of your crafting.