I have 70+ records that I need to add manual sharing details to, meaning I have to find each record, find the user, and add their permission level. Is there no way in bulk to do this using SF Developer, for example? This method seems really antiquated.
Every object has a companion Share object where manual shares are stored. The Object API names will be
for a standard object StandardObject: StandardObjectShare
for a custom object CustomOjbject__c: CustomObject__Share
There's more on these and other associated objects here:
StandardObjectNameShareWhen you manually share a record, it creates a record on the associated Share object, and if you're careful about it, you can create these records in bulk, with a flow, apex or using the blunt force method creating the records in a CSV file and uploading them with Dataloader, and
possibly Data Import Wizard (I don't know of any reason you couldn't use it, but I've never tried it so I can't say it'll work). Workbench would probably also work, and maybe Salesforce Inspector but I haven't tried those either, so take that for what it's worth.