After all that experimentation with Cricut masks, I decided to press forward with decals for 622. They were included on the same decal sheet as the flat car decals from Precision Design, and went on beautifully. I was glad I’d included an extra copy of the decal for the tender rear because I did indeed spoil one due to the steps. The left side of the tender also has a small amount of roughness, perhaps from insufficient gloss-coat (?); it looks worse with the reflected light for photography, and so, I’m hoping the Dullcoat will improve it.
There is nothing quite like lettering to make a model start to look real!
Pembroke:87 
Looking good René. For me, decals are a turning point where the model begins to take on its personality and come to life. Question: are the numbers integral with the lining as one large decal for the sides of the tender and cab? Thanks.
Thanks Jeff. Yes the numbers and lining are all one big decal.