How to keep it clean behind furniture that is hard to move, or in sofas

[DreamyCyanFinch]

Hello,
Can anyone tell me what you do if you have furniture which you can't move.Do you also end up with cobwebs and dirt behind such furniture or do you have a solution?
I just took apart my old sofa which was a bed sofa.In the part that comes out as a bed there was a lot of sand, fluff coins etc.
I did try and hoover in the gaps but do you take such things apart regularly?
What about under a fridge or behind a book case?

Thank you in advance.

Does it matter if you can't see it? Long handled feather duster?

I don't, although a radiator brush is quite handy.