You don't need to rub down the walls (just make sure they're free of cobwebs etc) but any glossed woodwork will need a quick rub with some fairly fine sandpaper.
Get a dustsheet to save your carpet, and some wide masking tape for around the edges (and still be careful, gloss is terrible stuff).
Recoating time will depend on heat and humidity - there will be guidance on the tins. You'll need to leave gloss for longer than emulsion.
You'll want a couple of brushes (different widths) and a roller with a roller tray (roller are pigs to wash out afterwards, but speed the job on the walls up no end). You'll want some brush cleaner for the brush you use for the gloss. And a stick to stir the paint. I also find kitchen towel handy for wiping up splashes and spills, and wiping down the stirring stick, and you want a plastic bag to put the rubbish in.
Fill and rub down first.
Emulsion second: cut in with a brush round the edges of the walls, skirting, door(s) and window(s), then use the roller. Once you're happy that the cutting around the gloss gives adequate cover and is dry, you can gloss. I finish emulsioning first as emulsion spray on new gloss (which is fragile even when it feels dry) is a pain.
Gloss last. Use less than you think you'll need on the brush and keep a close eye for runs and drips. Quick drying gloss is horrible as it's hard to brush out runs if you notice them a minute or 3 later. White spirit is good for getting rid of gloss drips on carpet but do it at once.
Between glossing sessions, you can wrap the brush tightly in clingfilm or a plastic bag; similarly, you can put the roller tray in a bin bag and secure it with a clip or elastic band.
I'm sure there is loads of guidance on YouTube but l learned to paint a wall before t'internet was ever thought of.