Thanks for the comment.
I'm guessing you mean 'Pattern along path'? Inkscape doesn't use brushes the way Photoshop, Illustrator, or even Affinity Designer, does, but you can fake it somewhat with other tools. I used Pattern Along Path to create what I had in the first post in the thread. My 'pattern' was essentially a few vertical lines all of the same size. I drew a contour line, then applied the pattern, and you can see the results in my first comment. It's really easy to do this, and it works pretty well.
I used to watch that guy's channel fairly regularly, though I drifted away from it a while back. It's a fantastic resource for learning Inkscape though, and I'd recommend it to anyone who wants to get more familiar with the software.
I've been working on a challenge map, so haven't really looked at this map for a few weeks, but I've been thinking about the pattern thing, and tried a few experiments tonight, just to see how they turned out. I threw together a pic of a few things I tried.
contours.png
The first pic (top left) is just a repeat of what I have in my map in the first post. Create a pattern of simple tapered vertical lines, then apply this via Pattern Along Path along contour line. Very quick and easy.
The second (top right) pic is with variable line lengths. The obvious problem is that the lines don't match up in the inner contours. There doesn't seem to be any way to offset where the pattern starts without leaving a gap at the start. Also, as the contours get smaller, there will likely be an issue if the pattern is too 'long'.
The third pic (bottom left) is an experiment with the Interpolate effect. In the first batch I tried, I changed the shape of the lines, so that they go from (slightly) facing left to right, then used Interpolate to fill in the middle lines. Afterwards, I bent the shape to fit my contour. For the 2nd batch, I used the slightly right-facing line from the first batch as the start path, then created a new end path. This 2nd batch didn't work so well. There were lines in the middle that were so thin you could hardly see them. I replaced them and used Bend to fit the contour. Overall, this method was time consuming and the results aren't great. Might work well for one or two short sections.
Fourth pic (bottom right) uses the Bend path effect. Basically, I created a couple of variable line lengths, then used Bend to fit them to my contour. This was relatively quick and I quite like the results. Although you have to manually create the variable lines and bend them to fit, it doesn't take all that long, and you have complete control over what goes where.
I'm not sure where I'm going with this (if anywhere!) but I'd been thinking of a few things to try, but just hadn't got round to experimenting until tonight, so this is my first attempt at trying out some of my ideas. I'm not even certain if long-ish contour lines are the way to go. Other maps seem to have little circles showing the relief, and that might be my next experiment. But... thought I'd show what I'd been trying, in case it's useful to someone else.