Please excuse me if you already know how to perform this, but I find it a useful and very fast way of updating programmes.
Insert a column and define the field name as "% Work Complete" (if the column inserted is placed next to the ID or name it is easy to check the entry is at the corect position). The % complete information can then be entered, supermarket checkout style, using the numeric keyboard. The % complete column can then be hidden, if required.
The copy and paste command is fine too but very often it can cause problems if the paste is out by one row.