I have 95% of the tools for a full service of a mechanical watch including crystal replacement etc.. I have built some movement kits and carried out minor fixes on others but I quickly realized I don't have the patience for movements (I had big dreams of buying sad sack ones and restoring them myself). Anything higher grade mechanical always goes to my watchmaker. But I have done many crystal replacements and as noted minor movement repairs etc.
For the family's quartz watches I keep an inventory spreadsheet--I do for all actually but for these I also note the battery (a good general tip) so when one stops I can see if I have the battery in inventory before opening it or I can order one up and not buy a cheap one. I can also take a dead battery out, park the watch and come back much later and know what I need... I always use quality batteries--Swiss or Japanese--might cost a dollar or so more (usually get them from H&W Perrin here in TO, order the common ones in batches)---I have NEVER had one leak, even after sitting dead in a watch for years. Avoid cheap, generic, watch kiosk, CT, Shoppers, big box, etc. ones (I have seen some of these leaking in the package). Mickey Mouse to high end quartz, treated the same....
Case back removal, I use the friction ball for all screw backs like GG noted (good memory). I have a proper tool but I have rarely have to use it. Just need to make sure the ball and case is clean to maximize friction. Can be hard to use without opening the bracelet. Can't use it on anyhting that still has a decal/sticker on the back as it will remove it (who keeps these on anyways).
Another small tip, I use an over turned frisbie or tray for anything like this. That way if anything is dropped etc. it stays inside...
I would send some pics, but I have COVID and the family has locked me away and all my tools and watch stuff is outside of my quarantine zone.
