How can people use N95 masks effectively?

We can’t rely on CDC at this time given they are still trying to get their act together along with the fed govt. Their advice is often conflicting and/or confusing. Eg: ordinary people should not use n95 masks. But medical professionals should. I understand we have in short supply but it’s confusing to say it helps in one place but not another.

Any health professionals on HN can provide objective thoughts. We know we can’t rely on this govt.

If one has access to these masks. What’s the proper way to use them?

1. should they be worn only when one goes out? 2. how much can they be reused? Days? Weeks? Indefinitely? 3. what are the benefits of using regular (non n95 masks) I one dosnt have the n95 masks? Is it still better than no mask when doing groceries?