The A and O of each workshop are screwdrivers; from these one can never possess enough. What in sold in tool shops as "Precision Screwdrivers" is unsuitable, since the blades are much too broad. What is needed for watchmaking, are special screwdrivers with much smaller blades. They are available in different qualities.
Normally the best should be good straight enough when handling watches. The problem thereby is, thank this can be very expensive, since a set of good screwdrivers (for example of Bergeon) can go easily into the three-figure euro-range. For flea market watches, this is much too expensive.
What however is to be held from cheap screwdriver? I made the experience that they serve quite well their purpose, however only, if you use a trick: At the latest before each larger action and if you notices that a blade became blunt, you must sharpen the blade on a strip sandpapier back into the correct shape and sharpeness. Thus one comes also with a cheap set marvelously over the rounds, without runining the movement and screw heads and nevertheless you've still got enough money available for further tools.
Admitted, the photo shows the lack here at quality of workmanship very drastically, but in practice with the trick I was able to work on any movement without damages. But of course, on a polished screw head or on a Lange 1 I would not dare to work on, and not only because of the screwdrivers.
Handling screwdriver differentiates itself fundamentally of what one as do-it-yourself enthusiast, where it is used to more around strength and power, than precision: The index finger is put on the mobile head of the screwdriver, it serves to position it exactly. With thumbs and middle fingers the stem is embraced and turned. Slipping is effectively prevented by the optimal guidance.
For the crude "Precision" screwdrivers from the tool market there is a use by the way nevertheless: The spring bars, in particular with metal bands, can be removed easily with these screwdrivers, and if one works carefully enough, one comes with them nearly just as well, as with genuine feather/spring bar cutlery to the goal. You just should not use it on a highly polished, golden watch, but rather on a rugged steel watch from the flea market.
Costs: Between 10 and 150€ per set (approx. 9 parts)