Revivex Treatment for a Western Mountaineering Micro Fiber Down Bag?

I have used Nikwax Down Proof wash-in DWR treatment on a Marmot down sleeping bag and several down jackets. No problem. Leaves a slick "water resistant" finish on the fabric. Definitely beads water. Didn't notice any change to loft of the down.

Key steps:

Front load commercial washer.

Expect to run several cycles in the dryer.

Put three tennis balls in the dryer with the sleeping bag. They bounce around and break up the clumps of wet down as it dries. Really fluffs up the down.

the water resistance of the MF fabric comes from a very high thread count and I believe is NOT treated with any DWR chemical from WM. So no, i wouldn't treat it with anything.

I wash my down bags/quilts with a little bit of woolite in cold water gentle cycle and dry on med/low or low until dry while tumbling with 3 new tennis balls. They come out very nice.

I use Revivex on all my down and GTX or eVent gear. It's the best spray-on DWR there is.

I wouldn't bounce tennis balls around. First of all they will scratch and afraid the DWR finish and the fabric.

Secondly, they're too hard and will smash a lot of down plumes breaking them for life.

I use balled up 100% Terry cotton and I only wash the bag if it is ruined otherwise (cat pee, bodily fluids, 20 years old and nothing to lose etc).

You are best off just wiping it down with a micro fiber towel and 6:1 water:woolite mixture.

My general rule of thumb is if I wouldn't wash my car with it I wouldn't wash my bag with it. Tennis balls are highly abrasive. Even if you don't agree that they smash plumes you need to know they scuff smooth finishes.

Also the dye on tennis balls is highly carcinogenic and comes off easily. Pass in sleeping on a bag covered in those dye particles.

I just washed my WM megalite a few weeks ago. I used a down soap and used Revivex to refreshed the DWR per WM recommendation on their web-site under the care instructions.

Your megalite and the op's bag are made with different fabrics with different inherent dwr properties. I dont believe treating the bag will harm anything, it is simply not required.