I've had a massive clear out recently and did look at getting in a pro, but decided to just bite the bullet.
Tbh my house is generally quite tidy, there were just a few rooms that needed a clear out.
Anyway, my tactic, that really worked was "4 boxes". I bought 4 large storage boxes on Amazon.
I had a box to put things to definitely keep, another to recycle, one to throw and an "undecided" box.
I just meant I didn't have to dither over the "maybe" stuff and plough on quickly.
Once done and the room sorted (and being in the mood to get rid of things) I found it really easy to go through the maybe items and make a decision re: their final box.
Then I cleared out the boxes (put things away, tip, recycling etc) and started on the next room.
The boxes stack, so when finished I've just put them in the loft (empty) for the next clear out (or house move).
Hope that's helpful.