With a grill that has wide gaps like your DB5 I use enamel gloss black brushed on to cover the whole inner grill then using Q-tips to wipe clean the chrome slats. Don't use acrylic paint as it dries too quickly. For grills with narrow gaps I just use panel line accent black, making sure it is applied to the grill whilst laid flat on the workbench.
Hope this helps Phil.
Cheers, David. ??
Gloss black enamel
Panel line accent