I picked up a Minox 35MB camera on a flea market, unfortunately it had the aperture blades clogged, so I had to disassemble it.
The problem was I didn't mark the position of the focus ring and front lens. Let's see how I found a solution.
What did I use?
*Unfocused Minox 35MB camera without the focusing ring.
*Focusing ring with it's three screws.
*Black insulating tape.
*Precision knife (X-acto type).
*Matte finish tape (Magic tape).
*Measuring tape.
Hope this will help, the basic procedure could be used in other film camera also.

Step 1: Provide a Focusing Screen

We should provide a translucent screen in the focal plane.
To do this we sticked two pieces of magic tape to the back of the camera to allow refocusing of a known distance object.

Step 2: Force Long Exposure

This is an aperture priority camera, it has a light meter in the lens that is partially obscured with ND filters depending on the aperture set. To force a long exposure that let us focus an object in our screen we should do two things, first put the film sensibility in the lowest setting (25 ASA).
Then we block the light sensor in the lens with some black tape. this gives us few seconds of exposure.

Step 3: Focus!

Shoot the camera against a bright source of light at a known distance, we used a light bulb at 90 centimetres (used the measuring tape), and rotate the front led until the image is sharp in the focusing screen.
Then you should reattach the focusing ring in the 0.9m position, slightly press the three outer screws and turn it to the infinity position.
spot something far and check for the infinity focus, remember you still have the light sensor occluded so it will be a long exposure.
If infinity focus is Ok you should take out the black tape from the light sensor.
This time you should do it properly, mark the focus ring position and loose the screws, take off the focus ring, take off the black tape from the light sensor and reattach the focusing ring in the marked position.
Now you have now a working miniature 35 mm film camera.
Load it and celebrate!