PREPARING PARTS FOR EASY DISASSEMBLE

One of the most vital steps in constructing a scale model is the initial assembly of the said model. This allows the builder to decide what needs to be done to make the model into something special. Once parts are 'snapped' together, they can become difficult to disassemble so they can be prepared for the next step. In this tutorial, I'll quickly demonstrate two easy methods to allow for a much easier disassembly of your test fitted models.
What you need :

1. The parts you wish to assemble and disassemble later.
2. A Hobby Knife (sharp is good).
3. Pin vise with appropriate sized bit (this will be explained later).

Method 1

This is by far the easier method. Take your pin vise and measure a drill bit against the peg. You are after a bit that is only slightly larger than the peg. Take the pin vise with the selected bit and gently drill out the hole. If done with correctly sized bit, a very small amount of the hole will be removed, widening the hole itself slightly to allow for the peg to slide in and out much more freely. Make sure that the bit isn't too large as the parts wont hold together, remember you are after a bit that will widen the hole only slightly.
Assemble your part and you will notice that they will go together much easier than before. To disassemble, simply grab edges that can be pulled apart and using your fingers, it should come apart once more to allow for addition of glues or putties for example. If you do find that the pegs or holes haven't been modified enough to allow for disassembly by fingers, take your hobby knife and slide the sharp side of the blade gently into the join. Gently rock the blade from side to side to loosen the parts. When doing this, if the top of the blade is to the right, make sure the bottom is to the left, then switch and repeat until the part pops apart again.

Method 2
Removing some of the peg allows for easy disassembly by increasing empty space in the hole which means a less than snug fit. To do this take your knife and gently cut away the peg at a 45 degree angle. Cut away about half the width of the peg at the top on a 45 degree angle and make sure that the cut reaches below the egde of the mating parts. This ensures that the peg is reduced all the way along, otherwise the section not cut away can block the hole at the very top which achieves nothing

Source