The Horizon LMS from SirsiDynix provides a utility to export marc records from the system. This is quite robust, except if your bib records are quite large and have a lot of subject tems. The following VBscript allows you to export smaller batches of marc records and skip over known bad records.
Another way to do this is to create a temporary table directly in the database using commands like this:
create table temp_export_bibs(bib# int)
select distinct bib# from item_with_title
where bib# != 8275 and bib# != 55870 and bib# != 72053
You can then use the /T option in marcout which lets you use a table of bib numbers to export.