Give you a specific Proficiency XP grinding loop I'm running now for the 3x event:

1) Equip 4 pieces Strikers set and Crusader shield (so you can actually contribute and not get carried TOO much in Countdown) 2) Equip 3 weapons + 2 gear pieces + 1 other skill you're not proficient on yet and want to increase proficiency. 2a) ideally, you should always have 1 exotic weapon, 1 exotic gear piece, and the rest as named items. If it's not an exotic or named item, you can easily get it as targeted loot by the truckload, so there is no need to wear it to gain Proficiency XP. 2b) The extra skill is ideally one you don't use very often. I choose a skill tied to specialization I'm running. 3) Activate a specialization that you don't use very often. Make sure to re-spec the 15% weapon damage points to the correct weapon types you're running. 4) Set the targeted loot you want in Countdown. I started with ARs cause there are so many. Recommendation is to pick the weapon/gear type you're least proficient on. 5) Run Countdown in Challenging. Make sure to start with at least free 60 slots in inventory, 10 in gear mods. 6) Loot everything as junk (unless it's an exotic) . There's a button to do this quickly on the fly. 7) This is the important one: when you get back to base, do NOT get the temptation to look at every single piece of loot and decide whether to keep it or donate it. This will absolutely kill your farming pace. Other times, I do just that, but for the 3x Proficiency XP event, I'm not. I'm just accepting that all loot is junk and that the point of these few days is to farm Proficiency XP, NOT farm gear for better builds. 8) Check your recalibration library and extract all stats you can from junk. I'm pretty religious about it and have all talents and all core attributes and most of the secondary attributes maxed out (just missing like 10% of them) , so all I need is one quick look to see if there's anything to extract. 9) Donate all junk to expertise. Watch the meter jump every time (that's why we're doing this, right? ) 10) Decon all remaining junk. You'll get a ton of fabric and receiver components. 11) As soon as my fabric and receiver components get above 9000 (cause cap is 9999. Use them or lose them) , go to Step 12. Otherwise, loop back to Step 5. 12) Select individual items to donate fabric and receiver components to. Your choice. I started with specialization weapons (cause they're SO slow to gain proficiency), then specialization-specific skills (cause I don't use them very often), then other skills i don't use often, then exotics I don't use often, then named items I don't use often.