Hi There,
I use some of Agraciers techniques as well as one or two of my own.
Firstly
I paint as a layer on the ed map all the necessary rivers using a reasonable river source image of the map your working on.
I paint this first layer in a bright colour like yellow, pink or teal or light puke green.
After painting the rivers using 2 pixals 3 pixals and sometimes 5 pixals I save as a copy roughly 5 times.
This will help with your Mymap_c, map_h, map_T ed_map_T and ed_map
As an example I place the high coloured layer on top of map_h. I then start to paint rivers using 1 rgb up to 100 rgb keeping rivers pretty uniform
example 10, 20, 30, 40, 50, 60 rgb etc for short distances starting at the ocean end of the river.
I use the above for very long rivers to hopefully create an undulating river down to sea level.
I have also used 5, 10, 15, 20, and 25 rgb same as above and that seemed to work well.
I then paint out the rivers like this over the highly coloured rivers layer it takes some time to do but you can see what you have done and what needs to be finished easily.
Once I've completed the rivers layer on map_h I fix it to the original map_h
Secondly, I then bucket fill a high coloured copy layer for rgb 0 and fix this on to My map_c blurring it a couple of times
After the initial work of map_h and Mymap_c I then run it through the coast align.
It does not effect your map_h painted rivers.
Thirdly, I then go into FMB + and look at all the rivers. Some will by quite ok other will need some work in the FMB+
I detail rivers in FMB + by working from the beginning of a river to the oceans end. It's easier to see the triangular humps that need to be attended to.
Also the banks can be widened depending on small open triangles from the original river cut.
Detailing rivers in FMB + takes some time and some times it good to have some other pairs of eyes to pont out what you've missed.
This way takes a hell of a lot longer instead of painting rivers as rgb 0 on map_h but well worth it in the long term.
I've recently been mapping Northern Borneo and am also working on a full Java/Bali map.
Cheers Kirby