create one-time backup files

Actually, to totally avoid interfering with a backup chain, it is best to use COPY_ONLY.  A Full backup will not interfere with transaction log backups, but it will become a new start point for any Differentials unless the COPY_ONLY operator is used.

If your backup chain includes Differential backups then you should do any "out of band" full backups by:

BACKUPDATABASE DatabaseName TODISK = '\\Server\Share\BackupFileName.bak'WITH INIT, COPY_ONLY;

GO