first welcome to our big Armorama family !!!! be glad that u are here and feel free to ask for help. Painting procedure is matter of personal preferences i believe, theres not wrong or right way in my earlier years i used to build and paint the main body and then add on all other items (tools, extras guns everything) Later till now i tend to build 90 % of the tank or vehicle , paint the primer , the preshading dark coat, and then the base coat . then i paint all the different coloured parts of the vehicle or tank . The only things that i paint seperately are stowage, tarps and carriage that is not directly connected with the vehicle , but i weather them together with the vehi , so there is a colour uniformity and evidence that all these parts have suffered same use and weather conditions.
For figures i have to say that i build them torso hands head and legs i paint the uniform primer and allover uniform colour and then the face and other flesh parts . i finish them correct any flaws on the uniform add the helmet or other equipment that i paint seperately and then i wash and weather the figure on the total , for the same reason as above .
for single and bigger figures , and not for dio purposes (meaning that acting as a figure painter u paint a single , mostly expensive, and special figure) depending on the era , pose, material of the figure and many other items u may have to paint seperately 1 or 2 hands or the head and add them last before weathering and washing once again. big figures equipment is always painted seperately so that u can deal better on the details.
Take car that u add in your painting habits priming with a good primer so that u have a good gripping surface for your painting. Also wash thoroughly the plastic or resin or anything , so that no particles are left on it that would destroy your painting ..
I hope i helped some, and anything else ..i am here.. WSe are all here
Costas
Greetings from Greece