Loctite is available in a number of "strengths," and there is an "instrument grade" that will retain but permit removal of screws down to #00 or smaller in size; but you are unlikely to find any but "automotive" grades in local retail markets.
The "screwlock" grade sold in auto repair shops might be safe on screws 1/4 inch or larger; but the "studlock" grade should lock a 3/8 diameter bolt tight enough to break the bolt without moving, once set.
A separate primer is virtually mandatory to get consistent results with Loctite, but is usually not used - partly because people don't know they should, and partly because these kinds of "retainers" should only be used where your don't really need them to begin with.
In the olden days before Loctite, instrument makers used to paint the heads of screws after tightening with "Glyptal," which is nothing more than a good grade of oil-based enamel. Enough will "seep under" the head to give some retention; but since most of it is on the outside you can pick it off, usually just with a fingernail, to remove the screw.
A few old instrument makers occasionally used a laquer made by dissolving a little rosin in alcohol to paint the threads of screws before installing. When the alcohol evaporates, it leaves a "slightly sticky" coating on the thread - if the part was clean enough before the application. A similarly applied beeswax coating was also sometimes used.
The problem with any of these is that you have to try one on a few screws before you can be very confident about what it's going to do. Replacement of worn or otherwise defective parts is the preferred solution.