Four small questions about brushing that most people have thought about more than they would like to admit. None of them is complicated, and none of them requires an expensive mouthwash.
Cold water or hot?
Either. Whatever temperature you can comfortably tolerate is fine, and water close to body temperature is the natural choice.
The idea that cold water damages teeth does not hold up. If a sip of cold water were enough to hurt, drinking chilled water and eating ice cream would be far more damaging, and neither is treated as a threat to teeth.
Water temperature mainly affects comfort, not cleaning. Hot water will not harm your teeth either, but it is not necessary.
Brush or drink first in the morning?
There is no wrong answer here, and the disagreement is mostly about something that is not actually a problem.
Bacteria do multiply overnight. Saliva production drops sharply while you sleep, which reduces their natural suppression, and if you breathe through your mouth it gets drier still. So yes, the bacterial count is genuinely higher first thing.
The concern about swallowing them is misplaced, because bacteria in the mouth are not a hazard to swallow. The mouth has plenty of its own resident bacteria whether or not you brush first.
What matters is that you brush. Whether you drink water first is a matter of preference.
Soft bristles or hard?
Soft, as the default.
Brushing works by mechanical contact between bristles and tooth surface, dislodging plaque and food debris. Hard bristles feel more effective but are more aggressive on the enamel and, more importantly, on the gums. Plaque does not resist bristles; gums do.
That said, very soft is not better. A brush so soft that it flops cannot clean effectively, and the usual recommendation is soft, or medium at most. If your gums bleed consistently during brushing, that is a reason to review your technique and your brush, and to see a dentist about it, not a reason to brush harder.
Bleeding that resolves within a few days of switching to a soft brush and easing off the pressure is usually just inflammation settling. Bleeding that does not settle is gum disease and needs looking at.
How long?
At least two minutes. This is where most brushing falls short, and where even good technique matters less if you do not brush long enough.
Consider what is actually being covered: the outside, the inside, and the biting surfaces of roughly thirty teeth, plus the tongue. Two minutes is not generous, and it is the number you should hold yourself to.
A built-in two-minute timer on an electric toothbrush is the easiest way to make this stick. Failing that, a two-minute alarm on your phone works just as well. What you should not do is guess. Almost everyone underestimates how long they actually brush.
The part that matters more than all of the above
Technique matters, but for most people the single biggest difference is where they brush. The two places people miss are the gum line, where plaque collects and causes most gum disease, and the back surfaces of the front teeth, which are easy to skip.
Angle the bristles towards the gum line, use short movements rather than long scrubbing strokes, and make sure every surface gets the same attention. If you are not sure whether you are missing areas, disclosing tablets will show you exactly where the plaque is.
None of this is difficult. It is just repetitive, which is why the same small mistakes persist for years.