As is widely known Excel has a very useful autofill feature.
Less well known is the Access 'equivalent' which allows you to copy the value from the same field in the previous record to the current record
To do so use the keyboard shortcut Ctrl+' (apostrophe)
This works both to fill an empty field or to replace an existing value
It works in tables, queries & continuous / datasheet forms
Of course you can also do this using copy & paste but that needs more clicks ...
A complete(?) list of keyboard shortcuts can be found here:
If you need to duplicate the contents of several fields at once, you may be interested in an example application by APR Pillai (Learn MS Access Tips & Tricks website). He uses the Tag property to Duplicate Multiple Fields in a record to the next record with conditional formatting