Here is info for SmartCopy: http://www.geni.com/projects/SmartCopy/18783
And the Discussions: http://www.geni.com/discussions?discussion_type=project-18783
If you are going to use the GEDCOM method please check your data before uploading the GEDCOM to Geni on these points:
Profiles without dates - They will probably be converted to private profiles and because of that cannot be merged by others than the uploader. So please provide at least guesses for at least one profile date (birth/baptism/death/burial).
Date format and date language - Please check day and month are in the correct order (try it with one or two profiles before doing a full GEDCOM upload).
Names in all caps - please only the starting letter for last name and name at birth in caps
Name at birth / Last Name - please do a small import (one or two profiles) to see if they are converted to the right fields (there are many GEDCOM dialects). Please make sure to on Geni name at birth is not empty for woman after the import.
They will probably go to the default language tab in Geni. If there are duplicate profiles in Geni with the names in another language tab they may after merging not be recognized by Geni as creating a data conflict.
If you are able to use a program (like Family Tree Builder or other program that can import and check a GEDCOM) to check your GEDCOM after you have downloaded it from MH please do and correct any problems it finds that you can correct before uploading it to Geni.
If you are going to do a GEDCOM import please also read https://www.geni.com/projects/What-to-do-after-you-have-uploaded-a-...
Importing a GEDCOM in Geni can by done by going to this page: https://www.geni.com/gedcom
Solving tree and data conflicts can take much time, so if you expect many duplicates it may be faster to use SmartCopy and copy only those families that are not already on Geni.
For searching Geni you can use https://www.geni.com/search/advanced (from Geni) or https://www.myheritage.nl/research/collection-40000 (from MH)
My personal guidance regarding GEDCOM vs. SmartCopy
-- if a 'spot-check' of (say) 4th-6th great-grandparents (e.g. via Google search) shows those profiles (and thus their descendants) don't seem to already be on Geni AND the 'source' is pretty well documented so that conflicts can be fairly easily resolved, then a GEDCOM import may be an efficient way to get those "missing" branches into Geni.
(Note: even if those '6th-great' grandparents are found on Geni, a Descendant Report (from the Actions menu button) can quickly show if the descendants already exist or if the GEDCOM import would be useful to bring them in.)
-- if there are questionable data or little 'supporting' documentation in the "source" tree, or one knows there may be issues to resolve anyway, then SmartCopy is often the better way to "bring in" branches ... for two reasons:
(a) Data can be corrected in the 'import' comparison before it is actually copied to Geni
and
(b) small family groups can more easily be checked for duplicates, merges, and data conflicts before going on to the next generation.
I would only use GEDCOM import if it is rather clear there are a few hundred profiles which do not yet exist on Geni.
A bit of "researching" before deciding to import a GEDCOM is *really* beneficial to everyone -- especially the one doing the import & cleaning up afterwards.