Just an afterthought about painting the sleepers/tracks first. Sometimes when the ballast has been added there’s a colour/tone mismatch between the two. It happened to me, so I dumped piles of finely-sieved garden soil & pastel chalk powder all along the tracks & worked it in with a dry soft brush to equalise everything…
Not saying it’s perfect – arguably I over-did it -but I think it was an improvement on what was originally there.