Run a tub of water and pour in some scent free detergent. Let the pack soak in the tub until it's thoroughly saturated and then agitate it to let the soap work into it. Drain and rinse and rinse and rinse. That's what I do when I've got bloody Badlands packs.
I don't waste my money on gimmicks. If I were going to do anything, first, I'd probably just leave it outside for a period of time. Then, after said period of time, I would maybe cut a few pine limbs, put pack in a tub, along with the limbs, and cover. Other than that, I'm gonna fill it with junk, throw it on and hunt.
Only time I ever cleaned mine was when it laid out in the barn several years with the mice and bugs.
Took it off the frame and then I soaked the heck out of it with permethrin and tied it up in a plastic garbage bag for about a week. Then hosed it off and took it to the creek for a thorough rinse. Filled a bucket with car wash and water and put it in the out back washing machine for about ten minutes. Put a hole in a lid for the bucket and stick the handle for a plunger through. Then you can get a real home wash done on about anything. Dump it out, rinse and repeat.
One more soaking with permethrin and hang it on the basketball goal to dry.
Had to do that again last year after I stuck a dead turkey inside there and must have been thousands of ticks crawled off it while I was packing it home. I'll take a bag to tie it up in next time.