I find it helpful to firstly do a tonal under- painting using a thin wash of pigment diluted with low odour white spirit. This dries quickly. I then paint the clothes with thicker paint using an alla prima ( in one go) wet into wet technique.
'A walk in the park' Here the under-painting was done with burnt umber.
'Chapel goer' Here the under-painting is done with ultramarine and light red.
Then the same colours are used on top but thicker with white.
'Chapel goers' Under-painting. They are standing in grass-that's my excuse for not painting the feet!!