Learn German: Wo sind die Pinsel? Es gab hier keine Pinsel! - Where are the paintbrushes? There were no paintbrushes here!

In English, we say 'there was' (singular) or 'there were' (plural). But German always uses the fixed phrase es gibt (there is/are) and its simple past form es gab (there was/were). The phrase stays singular regardless of whether it is talking about one brush or many.

Why didn't the word Pinsel change its spelling to become plural?

Masculine and neuter nouns ending in -el, -en, or -er (like der Pinsel) usually do not add an extra ending in the plural. You can only tell it is plural by the context and the plural articles like die or keine.

What case is keine Pinsel in this sentence?

It is in the accusative case. The phrase es gibt (and its past tense es gab) always requires its object to be in the accusative. Because Pinsel is plural here, the accusative negative article is keine.

Since the current lesson is about da-compounds, how would I add 'I painted with them' referring to these brushes?