How to target similar keywords

Say I want to create a niche site to sell toothbrushes. I have a list of low comp keywords I want to target, like:
"how to wash my teeth"
"how to wash your teeth"
"how to brush my teeth"
"how to brush teeth"
"how to clean my teeth"
etc.

The problem is that they are so similar, and there are multiple ones that basically have the same meaning.

So how do I target all these? I understand I have to put my keyword in the title + url, but if I make a separate article for all of these keywords my site will look spammy, with many articles covering the same topic but with different wording.

Or should I use a single article for keywords that are similar and try to rank that for all of them?

These are the similar keyword. So it is not recommended to have different articles. You don't need to use the exact match keywords on your articles many times. That will lead you into, over optimization and keyword stuffing.Since these are low competition keywords, you have to concentrate more on the quality of the content.

Google is smart enough to realise that all these are more or less the same / very similar questions.
If you end up with 5 articles all covering the same exact topic, you may get a penalty.

You can do a long article on how to brush your teeth.
What about then looking at how to brush your teeth with an electric tooth brush for the 2nd.
How to look after your gums for the 3rd.
Effects / benefits of brushing your teeth for the 4th and so on.

I think a single long article is the way to go. If you optimize the article for one of these, you can also rank for the variations.

If they are low competition, focus on article quality of QUANTITY..

those are just "stopwords".
so if you rank for how to brush teeth you "should" rank for how to brush your teeth by just having the word YOU in the content somewhere.
though, you need high DR(DA) for that to work.

What I'd do is create an article and then think, "What can I write about that relates to this article, yet isn't basically covering the same thing?"

You can then link from Article A to Article B, and/or Article B to Article A.

Example:

You create an article which is about: "How to brush/clean your teeth" (Article A)

You then create a second article about, "The benefits of brushing your teeth both morning and night" (Article B).

Within Article A you can add something such as, "Now you know how to brush your teeth, be sure to do this at least twice a day" - linking 'twice a day' to Article B.

Then keep branching off from here. Write an article that can relate closely to (and can be linked to/from) Article A or Article B, or both A and B.