I've done it.
If you search on MN you'll find loads of threads about kondoing - i love reading them 
The idea is that you do your stuff (and maybe the DCs if they're little) but you leave your DP's stuff. In theory he should be so impressed with what you've done that he follows suit 
For the stuff he leaves lying around, you could just designate one place for it all and ask him to leave it there? My mum once bought a nice wooden bowl for my dad for his birthday which was for his loose change.
I started with clothes and shoes then books then toiletries. Then paperwork. Then the kitchen. Then photos and sentimental stuff.
Clothes was just a case of looking at all my t-shirts at once and deciding which ones sparked joy and getting rid of the rest (charity). Then doing the same for each type of clothing : trousers, skirts, dresses, cardigans, underwear etc.
Toiletries I was quite ruthless. Either it was something nice in which case I started using it straight away. Or it was something I'd never liked and so I threw it away. You feel so much better having clear shelves and cupboards!
Birthday cards count as sentimental and you tend to do that last when you're a dab hand at separating out what brings joy and what doesn't.
For birthday cards for example I keep a selection but not every card. My parents always write the same thing in every card so I've kept a couple but not all of them.