Contrast paints are a new formulation that's gotten popular in the market. They are like a glaze with wash properties. The idea is that you can simply paint them over a white priming and you're done, all the shading is done for you.

I find the average results I see in real life to be underwhelming. The colors can often be patchy especially if applied to large flat surfaces like for example Space Marine armor. What is more is that contrast paints only contain one shade of pigment and the darker or lighter portions on the model just relate to pigment concentration. I prefer to shade and highlight by adding different colors to the base paint. I find that it offers more control and greater range over the colors. The control relates also to how highlights are placed. Many people either skip them entirely by relying on contrast paint, or they copy the modern GW Box Art style which highlights pretty much every single hard edge rather than trying to give the impression of a light source. I like to give the impression of a light source.

For traditional touches, blacklining is a practice of tracing a thinned black or near black paint on the borders of different objects of the mini to help give them definition. This can be especially important when painting in bright and saturated color schemes to keep them from assaulting the eyes with too much brightness.

I underpaint, which is related to mixing for shading but means to paint certain areas a particular color in preparation for another color to support it. For example Caucasian skin is usually a red-brown or purple before the first actual flesh tones go on.

Sometimes it's just things I consider absolutely basic like basing a mini at all in any way. All I my minis are based with texture in some way (any you see in my history that don't have basing texture were specifically requested such by other people) and have at least basic drybrushing or flock. A lot of people just paint the bases now, or simply just leave them bare.

I also like putting segmented colors, camo patterns, or other simple freehanding on minis. This draws a lot of attention in real life as many people are so used to just contrast painting that they never learn fine control and as such never even attempt freehand.

I do have a few paper copies of older painting books I reference along with various PDF scans. All the the exact paint recommendations are out of date, but the general concepts are still valid.

I partially blame army bloat and the FOMO treadmill in Warhammer 40k for creating unmanageably large armies that cause people to treat the painting as a chore to be finished with rather than something to enjoy and get better at.