Hi Barry I hope you don't mind my adding something here?
I've been following this thread for some time and dipped my toe in the water using inks for some wagons but had been reticent to do an actual coach. My normal procedure for most carriages is to T-Cut the sides to get a bit of gloss (not too much mind) and then weather with washes and powders to bring out the detail in door handles, recesses etc.
I decided to have a go at a Hornby Thompson Brake (didn't take a 'before' pic). I applied one coat of black ink and decided it wasn't enough for a coach that spent a lot of time in the smoke, so added another coat. This was a mistake as I'd overdone it, and it didn't seem to want to wash off easily. Soooo I decided to have a go at gentle T-Cutting after the 2 coats of ink had been applied and was pleased with the result. The 'before' pic is a Composite but included for comparison as they were both exactly the same colour out of the box.
Note I've only weathered the side. The underframe and roof are yet to be done (probably the wrong order but I was experimenting). I'd add a few people but those footboards are so delicate I can't seem to get remotely near dismantling the coach without causing major damage.