Honestly it depends what your dry brushing for all the tree trunks I make as well as the brick walls I cast I like painting the crevices with watered down acrylic and then once dry I start dry brushing stuff. I use a rag and a really beat up flat round brush to do the dry brushing. I take a little bit of the acrylic i am going to be dry brushing with and i dab it with the brush i then apply it to the pallet i am working with and finally dab it on the rag then i go to town on what i am dry brushing.

For vehicles and figure I like taking the smallest amount of paint and adding it to the area i will be drying brushing and then i push that paint around spreading it and brushing it everywhere i want it. this way it breaks up as I want it, for this as well i use a way smaller brush so i am working with a 3 brush or what not. hope this helps hit me up with any questions bro!

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"All things are subject to interpretation whichever interpretation prevails at a given time is a function of power and not truth. "
Friedrich Nietzsche