Having the courage to take baby steps will get you there….be brave.
plus when peed off and you think you cannot do better walk away give it a week then look at it,sonetimes being too close stops you realising how good/better you are,I always say try something cheap throw everything but the kitchen sink at it,and learn
couple of quid
Unboxed
glue for texture
two shades of blue and white mixed with blue to fade
brown and red brown for rust
transparent green browns black for dirt
just heap it on
add plant growth, who needs soil
reference pictures always help
suitable layout
plus IF when you test on a cheap item,and you are certain it is a fail, it is also perfect to have another go,the original colour is inconsequential. I have been known to have a go at the same thing a couple of times to see how something might have worked out with a different colour, and of course no 2 wagons are likely to weather exactly the same anyway
Basically
if the item is too shiny, add powder, rust or black,are easiest
if too loud, a transparent wash,brown or black, e.g pure white sonetimes just looks wrong
if the colour,l.e a powder can be rubbed a ruined try a dulcote varnish
if the item is cheap, throw the wife’s makeup

okay NOT lipstick eye powder or blush powder,
when adding a wet finish stand the item up the correct manner and ensure any liquid falls as per gravity.
IF a static building ground the building was grass, or ballast,because floating buildings always catch the eye,unless they float in real life,eg sheds are sonetines on timber bases and propped higher than ground level,so floating is acceptable - to sone degree.
If weather a rolling item wagon, loco, pls pls darken the bogie, in fact many bogies look better for not being plain plastic.
Many successfully use hard wearing enamels, I prefer acrylics, they need a little more careful handling but imo the colours tend to be more realistic, photograph better, of course specific colour matches usually accommodate for this so an enamel then can be the better choice. I still find acrylics more forgiving, but I know good model,ers who will argue the opposite and show their own work to prove it,
Work with what you like, and learn the necessary techniques to achieve the finishes you like, and buTest them especially if using say an airbrush rather than buying loads of colours and finding you hate them. It happens.
I personally never ever repaint a loco a new pristine colour, too much like hard work lol.I prefer old weathered for the very reason that it is more forgiving.
I personally have several mistakes along the way that I have kept, they were my learning curve, well plus the fact I am pretty lazy lol.