I would add the suggestion that you set the PM option (Preferences/Files) "Allow modificationof files on Camera Disks" to disabled (as is the default I think) when you open your CF card in PM contact sheet directly. That way, you can still Tag and Rate the photos, but the Tag or Rating wouldn't be written to the file itself (PM will just remember the tag or rating until quit). It's never a good idea to write to memory cards with the original files as some cameras, e.g. EOS 5DmkIII, give an error with a card that has modified contents on it - I guess they dislike the XMP files or something - and it minimises any chance of corruption.
Without writing to the CF card itself, you can still easily open its contents as a contact sheet (PM - File/Open Contact Sheet), browse the contents, tag or rate the files you want, and Copy only those tagged to your HDD (use View/Tagged or the little star rating filter/colour rating filter widget in the lower right corner to filter view, or you can easily select only files with Tag or specific rating/colour using Edit/Select...).
PM's Copy dialog is nearly as powerful as the Ingest dialog, as it can also use Variables to automate folder naming (I use {dats}_NameOfShoot to automatically create easily sortable folders like 20150911_NameOfShoot depending on the capture date of the photos), it can add IPTC data to the copied photos, as well as add DPI, embedd colour profile etc.
I still think the best and safest (and recommended) workflow is to Ingest the whole card and cull the photos form HDD, but there are some occasions where I use the workflow outlined above.
