I don't need to use shampoo in order to get it completely out of my hair, but I have noticed that it takes me longer to get either of them out of my hair when I co-wash. I actually started lo-pooing every third wash or so because I'm afraid of build-up, but only because my hair is so fine and so easily weighed down. I never really saw any evidence that it was building up in my hair when I just co-washed.
2b/2c, fine, thick, normal porosity/elasticity

Current routine: co-wash & detangle with AIA Coconut CoWash then RO. Experimenting w/AG re:coil, DCVF & All-Nutrient Hair Proteinizer.
Love: AO GPB, KCCC, PBH Gelatine Goo, ANHP, CNPF
Like: GDL, FSG, honey, HETT, JCNS, DCVF
Hate: glycerin, mineral oil