Don't try this at home (but I did and it worked fine!)
My Imago sees heavy, heavy work. It's my standard go-to-work bag, usually my personal item on planes, and a day bag when traveling in urban or not-so-urban areas. So it's been looking a bit grimy these days. I've carefully washed the cork insert successfully with plain water and a wash cloth, but when I got back from my most recent trip, I decided it was time for a real wash of the whole bag.
Obligatory disclaimer: I know that this is not the recommended way to wash this bag and has probably voided the warranty. (But candidly, I can't imagine this bag not lasting forever--it's that well made.)
Okay--disclaimer out of the way. Here's what I did: I washed the bag in the kitchen sink full of water and a capful of Woolite. After gently swishing it around, there were still some areas that seemed grimy to me. Then I remembered that I had just discarded and replaced the cleaning insert for my Clarisonic. (For those of you not up on girly appliances, the Clarisonic is a bit like a much, much gentler version of the Sonicare toothbrush, but for your face--it has a large circular head of soft bristles that vibrate--not spin--and clean your face thoroughly but much less abrasively than using abrasive scrubbing cleansers. The heads are supposed to be replaced every three months or so, and come in regular, sensitive, and delicate versions. Mine is the sensitive skin head.) So, I retrieved the discarded Clarisonic head, turned the unit on, and gently moved it across the face of the ballistic nylon. Success! Then, tentatively, I went over the cork insert. And that worked, too!
I rinsed and dried the bag flat, and I swear it looks good as new. Now I just need to order some Nikwax to restore the water resistance of the bag.
Final disclaimer--do this at your own peril. It worked for me, but your brush head might be somewhat stiffer than mine or you might use more pressure in cleaning than I did. (Although, honestly, if it were, you'd abrade your face with it!) And, whatever you do, don't even think about using a sonic toothbrush. Way, way over the top!!