I've been making inroads in some of the "dead ends" of great-grandparents.
For most of them, they were born or were married in the late-18th/early-19th century, right when Tanguay ends, so there's no easy documentation to peruse. Instead one has to start relying on Drouin, which is actually quite good, EXCEPT the records are all hand-written and (of course) in French, so you have to deal with crazy penmanship and translation issues.
Furthermore, all of the entries are long-winded repeat information that could EASILY have been compressed into a line on a spreadsheet :-): "On the eighteenth of November in the year of Our Lord, seventeen hundred and ninety-two, after the required three banns were read at the parish in the church on the previous three sundays, we record the marriage contract of Jean-Louis Somelastname dit Someothername son of father Louis-Jean and mother Marie-Ernestine-Desanges Hermaidenname dit Herfathersditname; the parents residents of this parish, etc., etc.," So it can be rather difficult to untangle, especially if the recording priest wasn't exactly a model calligrapher.
So, last weekend I worked out the Daigle branch of the family, starting with Marie Daigle (3ggp) back several generations through Tanguay It hasn't been without some frustration. The first French-Canadian Daigle (D'Aigle) was actually Austrian (as in from Vienna), and like immigrants from all over the ages, had some trouble working out what his name was supposed to be in his new country of residence.
Before "Daigle" became his family name, he went by D'Eyme. This caused me an entire morning of frustration because Tanguay recorded two different marriages, both to someone named Marie-Anne.
One Marie-Anne - Croteau, and the other Marie-Anne Proteau. If you look at the Drouin record, it's hard to tell in the priestly scribbling whether the necessary-to-be-established first letter is a C or a P.
Of course - at first - I wasn't aware of the Daigle-D'Emye alias, and this caused problems because the marriage record (Marie-Anne Croteau) has a date of 1685 (which isn't listed in Tanguay - I suspect he omitted it on purpose because HE was also confused). This is a problem because Marie-Anne's father's marriage was in 1686, and while there's no baptism date for Marie-Anne, she'd be no older than 9. The marriage record DOES say she's 19, though, so there's a mistake somewhere.
OK - so Tanguay goofed - or so I thought, and I went through and annotated everything (myself making a mistake because I didn't read the entire date in the marriage record, putting down 1680 - "seize cent quarte vignts" missing the "cinq" that followed), backed out of Marie-Anne's father's record (which got complicated because HIS father IS a great-grandparent on another line), etc., etc., etc.
Then looking at the other family trees available (and finding my 1680/1685 error) realized that Daigle was D'Eyme in the original record, and came to the (still incorrect) conclusion that someone had attached the record in Drouin to the wrong person. ARGH! Undid EVERYTHING, deleted the notes, and started over looking for the REAL Daigle marriage record.
One problem is that I've become less interested in all the things that other ancestry.com people attach to their ancestor records because there's a LOT of "cutesy crap" that really has nothing whatsoever to do with the person but is more some weird faux-fantasy application to what the contributor things the person was like (I get the impression they see these people as inhabiting Harlequin romance novel covers more than being people tied to their surroundings out of day-to-day desperation.)... But, sometimes there are very useful gems in there, and I should be more diligent about weeding through it. Turns out someone HAD made a notation with the VERY critical information that Joseph Daigle - when he arrived in Canada - had used the name Joseph D'Emye. Looking THAT name up in Tanguay found the Proteau marriage (aha!) and the correct link was made.
(So Tanguay DID make a mistake: Marie-Anne Crouteau did NOT marry Joseph Daigle and they did not have a son André. André's mom is Marie-Anne Proteau.)
I find it weird that more people haven't delved into Drouin, including Ancestry.com. Most of the time the "automatic" metadata is next to useless: Jean Smith, born 1750-1850, married 1750-1850, so you tend to hit "Ignore" for those references because they're just too vague. In reality the actual dates ARE there - they're just in the handwritten text, and you have to work it out. I suppose it's still too much to hope that optical character recognition has improved to the point where it can handle handwritten long-form prose in French, but it would be a start!