I've played around with cheap scopes a little. If your time is worth nothing, go ahead. They all come apart a little differently, but some are staked together and it can take more effort than it's worth. It's usually some variation on remove eyepiece, remove turret adjustments and, sometimes, the turret and remove the erector assembly/reticle holder inside. They're all different.
As for reticles, spider silk has been mentioned, I've seen tungsten wire used, you could supposedly get it in sizes smaller than silk. It was mentioned in a project for making an optical micrometer for measuring star spacing on telescopes. Amateur Scientist, I believe. Probably the source for that is no longer active.
Weaver scopes had chemically milled reticles made from sheet brass, some of the other makes did likewise. All you'd need there would be a stencil and some photo resist, along with the etchant of choice. High end scopes frequently have etched glass reticles, you can do fancier patterns that way, too. Preferably anti-reflection coated afterwards. All this wil cost you a lot more than picking up a used cheapy at a gun show, though.