The first is from 'FineScale Modeler', and covers the types and main brands of modelling filler available, as well as offering a mini-insight into using them. I recommend it.

It's an excellent article- and mostly pictorial

https://finescale.com/how-to/articles/2 ... your-hands.
At the same time, this video on using Milliput is really instructive. I'd say, it's well worth a few minutes of your day (or night

I've started this thread in 'Painting and Weathering', as - at a glance- I couldn't find a more suitable location.

Do check 'em out.