sand it,wash it with sugar soap and follow the instructions that go with the floor paint as to primer ,uc or whatever
i might be inclined to use a primer if the after sanding it is a bit patchy
ps a neat trick for caulking the gaps is to mix some of the sanding dust with animal size glue .spread it and press it in with a plastering trowel dont worry about bits on the surface ,dry and then give a final sand.
that mix sands off the surface easily unlike pva mix or fillers and soaks up paint to become strong and flexible.it lasts much better than squirted fillers etc etc . the edges between skirting and floor are best done with decorators acrylic caulk which has a good coefficient of expansion to allow for movement ,if you have a dulux decorator centre nearby their own brand stuff is cheap especially if you get a box of ten(if you are doing a whole house it will get used before it sets in the tube) and quite good
ps use a roller on a stick to do the painting.
grease is your enemy on floors ,gravey,old make up ,candle wax etc etc will mess with paint so good prep is never wasted time.
ps i know you dont want to fiddle with it too much but sanding will proved a key for the paint which a quick wash will not ,it will last a lot longet and look a lot better with some prep.
a coat with a roller on a stick is very quick but some extra hours time on prep adds years to how long before it starts to look like it needs redoing
pps if it is undamaged(plumbers and sparks can be messy) tongue and groove you can omit the between board caulking but still do the edges to avoid drafts
a industrial floor sander will do it ever so quick if you hire one and get a few bands of 40 grit and a few of 120 gt about 20 quid from jewsons for 24 hrs + maybe another tenner for the belts you use(other hire firms might have different prices
two passes rough two fine should take half a day ish.by hand sander it will take a long time.you need ear defenders
Dpack, you saying dark oak stain was used to give an air of age to furniture reminded me of the loom I had made for the 17th century village in Gosport Hampshire. I had a choice of pitch pine or ash, so decided on ash, which of course is white. Lots of people said the loom couldn't be of the right period because it was so pale, but they had only seen even Victorian ones that were of course the original rather than reconstructions. When they were made all of them would have been pale wood coloured as they would probably not have been stained.