Here is a radical thought- try a"white" undercoat.
Some old school enamel blue/grey. Thinned to about 50%. Pipettes sourced from e-bay a 100 for a £5 makes this easy to do. The fact it dries slower than acrylic is an advantage.
This is washed on with a large brush. Enamel being oil based flows differently to water and finds the shadows easily - well that is my view anyway - and how Army Painter works.
Now its over to the acrylics all thinned with Flow Enhancer. A dark blue for the Puttees.
I used Hull Red for the rifles., and Black/Brown for the boots
Desert yellow / sand colour for the helmets
Final bits, the scabbard, linen back, and metals - job done.
A little bit of basing! and there you go.
I am just about over the busy period in Feb, so it will be back to the brushes shortly.