Thanks, Nomad. . .I hope all is well in Scotland. Some of these are in the style of some of my favorite masters--the second one you like is a Claude Lorrain; another one is a Jan Both and an Asher Durand. The first painting, the one with architecture, was done by first tinting the panel with a very slight glaze of burnt sienna, what is called "imprimatura." Then I painted a detailed verdaccio (same concept as grisaille) using raw umber green shade (Winsor Newton brand) which is a transparent earth tone. No white paint or anything else, just that color. When dry, I added color using transparent colors in the dark areas, more opaque in the light areas. For some of the light areas I let the light warm area of the panel show through. I sometimes do quite a bit of glazing, if required.
The others were painted in the "indirect method." Both these methods were used by masters like Rubens and others. Here's a great illustration of these methods by Gamblin Paint's website: https://www.gamblincolors.com/indirect-painting/
For these miniatures I work flat on a table. I use a liner brush for fine details. Takes a little practice and a light touch but they are fun to do. I feel like they make larger paintings seem easier after working so tight.
I hope you are working on some beautiful Scotland landscapes!