Gotcha. A flow map is just a vector/normal map, but in tangent space.
I just checked and it is limited to vertex painting, but there’s a reason behind that. Brushing needs a bit of distance between direction changes to look good.
The single-value brush direction and the vertex brush map are both in object space. The flow map tutorial you linked is mostly a work-around for someone working in tangent space. You don’t need to go to all of that trouble since the shader supports object-space brushing, which lets you use a single value with some slight variance to get a uniform brushing look. Before you go too far, I’d actually try the single-value parameter or the vertex map. Vertex paint maps can be created in photoshop and imported, so you’re not stuck painting in the editor.
I’ve completely edited this post a bunch of times as I worked through the process of remembering how it works, so hopefully I didn’t confuse anyone.
Regarding the rest of your comment, there’s no version number or facility like that. All we can do is provide a file and Epic do the rest. One thing you could try is upgrading your editor to 4.19 or 4.20.