When I paint my ancient, fantasy or medieval era 1/72 figures; for the shields I cheat a bit and use commercially available decals for any artwork or other patterns. Decals for 28mm figures tend to adapt well to the 1/72 scale shields. For flags, you can cheat there too and some folks just substitute paper cut-outs.

For the rest, it`s all in the brushes, brush tip/head size, your fingers & wrists, good eye (and for some a desk magnifying glass). I used to paint figures direct on the sprue, but now individually hold each little guy one at a time for better control. Some folks will place a figure onto a bigger bottle/jar with blu-tac (if their hands aren`t steady enough or for better control I suppose).

YouTube is actually a great resource for painting tips and demos whether you`re into 25mm or 54mm figures of whatever era. There are many great videos there.

Be prepared to make mistakes along the way, but you will improve with time. At the end of the day, it`s a lot of fun, and also for me very relaxing!

Nice tips
Life doesn't distribute talent fairly so knowing your limits is a great step. I don't buy the monkey and typewriter (word processor now) theory. My virtuosity on the violin lasted milliseconds and the monkey would have got there with fluent quartets long before me. Best quality materials and tools give a modeller a fighting chance to improve so ditch the "a poor workman blames ...." saying. Magnification and macro photography are 2 great adjuncts to jolting you out of self satisfaction. Go round shows and buy a few choice examples you think are good and better them. If you are good you can better the best. Tiny figures they are but the painting needs planning and should be thorough so that detail is not obscured or the colours look wrong. Expect to never be satisfied with what you do because none of us are and don't capitulate.
finally
I always blame a crude overall effect and resistance to my fine detail painting techniques on poorly designed figures There is always some saying about a silk purse and sow's ear to salve my ego.

As others have stated, magnification is your friend. As well as desk magnifiers, consider a head visor - the very affordable one from Rolson is one of the best purchases I've made for these ageing eyes.

https://www.amazon.co.uk/Rolson-60390-Loupe-Magnifier-Visor/dp/B001MJ0JW2

https://www.youtube.com/watch?v=eaRkIsDJDK4