Flow medium for acrylic painting

Well, it works - but you may need to change your brand of acrylics to one that flows naturally. There are various brands and variations of brands on the Jackson's website, and others of course - but they probably have one of the largest ranges. If the paint is sinking into the paper, it's not likely to be the flow that's the problem, but the paper - are you using cartridge? A paper that just guzzles the paint, water and medium is likely to belch appreciatively, stop your flow, and ask for more. So I would suggest - switching to a flow-type acrylic of the type normally available in pots rather than tubes (although System 3 is quite liquid), maybe using a harder-sized paper, even a sheet of Bockingford might be more receptive than cartridge, and spraying it with water before you start. You will find your lines feathering if you use too much water, but at least the paint should flow; and you may find it possible to adjust your technique to allow the initial damp sheen to dry off a bit. The short answer is that flow improver does work, but may not be the answer to the problem you identity. NB - I have no experience with Interactive acrylics, and don't know if it would help to use them - but on balance I doubt it.

Peering myopically at the label on my bottle of Daler Rowney Flow Enhancer, I see it suggests mixing it with the medium, or with the water used for painting - 1 tablespoon per 500ml. No reason that I can see why you couldn't mix it with the paint itself, but I think I'd be more inclined to mixing it with the water to achieve the results Keora is after - and again, on a harder-sized paper than the one she may have been using. (Why, by the way, must the print be so small on these bottles and tubes?)

Good idea (the gesso). W & N artists' acrylics are quite fluid by comparison with some other major brands, so with a bit of water, flow improver, and perhaps working on the gesso quite damp, you should certainly find an improvement.