Tag the product specific sections by putting them in Rich Text (or plain text) Content Controls. Use either the Title or Tag properties for each of these CCs to show what product the section relates to.
Then you can use a macro to quickly show/hide or permanently remove the CCs chosen as not relevant. A basic example of this is shown below
Code:
Sub ShowMe()
Dim aCC As ContentControl
For Each aCC In ActiveDocument.ContentControls
If aCC.Title = "A" Then
aCC.Range.Font.Hidden = False
Else
aCC.Range.Font.Hidden = True
End If
Next aCC
End Sub