Hi
Stu, I don't think I'll be much help since switching to an
airbrush some 40 odd years ago.
For armour I use base colors like olive drab, German grey, dark yellow, desert yellow, brown and pea green over a primer of either white, black or brown. It covers large areas faster than a paint brush and I'm too lazy to wait for coats to dry and afraid to agitate the previous layer brushing on the next layer. You see with an
airbrush the paint is laid on top in a blanket style. Also the solvents used dry quickly. If I brush paint, cobwebs would have formed on my kits already as most know I work at a snails pace.
However I will use a paintbrush for detail painting and weathering. Specific colors here are not necessary because I mix from a set of primary colors to get the shade I need. I use any form of medium but must remember what solvent or thinning liquid is required for each application. Lately Vallejo or AK is what I use, oils was my previous but now and then I will mix to get the effects I need.
Spend time experimenting with the different mediums as they produce great results when used altogether. Or you can find a medium you are comfortable with and stick with it. If anything goes wrong just re-do it. I realised early on when breaking a part it was no use fuming over it as the kit was in pieces in the first place...just stick it back.
Cheers,
Richard
PS: All suggestions above has been given freely and I will not be held responsible for any mishaps that should occur while executing the hobby.