PC browser is the fastest but can be done with mobile browser but very slow
Fubar App doesn't work for this, at this time.
LVL 71 requirements 10k re-invites in the search tab you want to get 3k or less searchs to get the most of it so you need to narrow the search field a bit. 3k limit is due to the search tab can only show upto 100pages of 30profiles.
Search Tab
goto extras list check the box for Has Primary Photo, very important
Choose a gender
Then choose a an age group
Then chose a country with 3k or less
Go to the last page, for instance if there is 3k profiles, go to page 100, and work your way forward. The last page are the profile who have been gone the longest.
Open as many profiles your computer can manage in new tabs, hit invite buttons on each profile,
switch tabs and repeat until you have all opened profiles.
Some browsers will let you switch tabs using:
Ctrl + tab, going one direction in tabs.
Ctrl + shift + tab to go oppisite direction in tabs.
Close profile tabs, I use the ctrl +w to speedup that.
Go to next page and repeat the above steps.
if the country has more than 3k profiles, you narrow it down by relationship status.
if the relationship status, especially United States country of origin, is over 3k you can further narrow by lvl.
If the profile picture has a little green ball, this means they are online now, and most likely the profile before it are no elligible for re-invite.
But some time the search function of the server is a little wonky.
If you have a decent computer and internet connection you can do 400/hr easily some can do 600+
Ok to do these achievments, it is as follows on PC:
Search Tab, chose under the extras section Has Primary Photo & Search Friends Only then hit search.
Go to last page of the list and work your way back to first page.
Open page for each profile, look for a Pink tab, that same invite them back.
To keep track so you don't open the profile again, rate and like, and at the pime of this post chose Naughty or Nice for the christmas holiday chase.
Easy peasy did 100 in 20min.
At this time this can only be done on pc, and on mobile broswer not on Fubar app.
UPDATE: It seems you get more invite possiblities if you chose to break up the search I described above by female or male.
Have 500+ at the time of posting, and if you go to the same profile again to re-invite wait over 24hrs, 48hrs or so would be best.
More helpful strategies
I use the search like mentioned above, but when you go to the last page the search can only go back 100pages.
With 25 profiles per page, you will only get a max of 2500 and that is if you are lucky that all of them are useful.
So I search using key words, like colors, eyes, lady or other common words used in names.
And I further get them to 2500 or less buy search female or male, friends, with primary picts.
I know there is other blogs out there that describe searching longtime member's friends.
I don't do that not have the time.
I'm around 1300 re-invites (i've been slacking), there are 4 members who have already did all 5k need to for all re-invite achievements.
http://fubar.com/achievements_achievers.php?a=2212
Have fun all ;-)