So I picked up a used DriMaster for $280 on ebay last week to give it a try with my portable. It got here today and I tried it on my basement microfiber couch and office chair. It definitely uses a lot more water than a regular upholstery tool. I probably used a good 9 or 10 gallons of water between the sofa and office chair. Although it used more water, it definitely left the furniture drier in my opinion compared to my other upholstery tool.
It's a lot more ergonomic, but to me it still is kind of heavy. This is the old DriMaster I got though, not the latest so maybe that has improved especially with the optional handle you can now get. I feel more confident doing upholstery now with the DriMaster compared to my old tool. I would not hesitate to clean cotton with the DriMaster but I sure would with my other tool. The guy I bought it from told me I would toss away my other upholstery tool once I tried the DriMaster and he was right.
Bottom line is it will work with a portable, but expect it to use plenty of water. Even with the metering valve not cracked a lot. Having it leave the fabric drier and be more ergonomic in my hand, I don't mind filling up extra buckets at all.