This question already has an answer here:
How do you go about cleaning out dust and other dirt/particles/chunks of food from under the keyboard keys.
I know its possible with compressed air, but what other alternatives are there, apart from removing all the keys from the keyboard and cleaning it, or vacuuming it?
The compressed air I'm talking about is something like this:
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
I've used a product called CyberClean. It's a Swiss product that is kind of like Gack if you have heard of that. It sticks to it's self but not to the keyboard and collects lots of dust in all the weird nooks and crannies that computers have. It works well for dust, crumbs, hair and lots of other small stuff and can wrap around irregular objects. It is not oily and does not leave streaks even on monitors but if you try to force it in too small of a gap pieces may come off. Then you just have to carefully dab at it until the small pieces are collected. You can buy these in small baggies or in little tubs. A small baggie would work for weekly to monthly cleanings of a laptop for 1 year probably.
For a separate keyboard, invert and shake. The same, but much more gently, for a laptop that is shut down. A cheap paintbrush is great for cleaning between the keys, before the dirt gets underneath. Air pressure is just as likely to drive dirt into the keyboard as out of it.
Though you state you want to avoid removing keycaps, some may may be popped off easily using a thin wire hook or nylon thread looped underneath... but some laptops require disassembly to remove them.
