Assuming you mean, are the words "clean those brass" adjectives, the answer is no, maybe, and yes
Clean is a verb.
Those is a demonstrative pronoun. (Some people might call this a form of adjective, as it is a modifier.)
Brass is an adjective: a brass Trumpet, a brass bookend. Note that brass is also a noun in some uses: the brass on that uniform is shiny, the brass in this orchestra is very good
The adjectives are clean
clean
There are no nouns for adjectives bro. There's not going to be a noun for blue so there's not going to be one for those.
You can clean a brass telescope. Over a duration of time, brass starts to oxidize. To remove this, can use vinegar and salt. You can also use a concoction of chemicals that is premade, usually by a company that specializes in brass.
This That These Those are some demonstrative adjectives
http://home.howstuffworks.com/how-to-clean-furnishings3.htm
There is an effective way to clean brass door knobs. The first thing they need is to determine if the knob is brass plated or solid. If it is plated, use caution in the cleaner that they use.
Hopefully, these adjectives: clean, pleasant, popular, inexpensive, accessible, roomy, efficient.
The adjectives in the sentence "He ran off to put on a clean shirt" are "clean," describing the shirt. There are no other adjectives present in this sentence. The focus is primarily on the action and the state of the shirt.
That, This, These, Those
Brass will oxidize and turn greenish. Moen and Delta have PVD brass finishes which are more resistant to corrosion.
To clean brass, mix equal parts vinegar and water or use a commercial brass cleaner. Apply the solution to the brass using a soft cloth, rubbing in circular motions. Rinse with water and dry thoroughly. Avoid using abrasive materials that can scratch the brass.