The problem I've run up against is the DNA testing company with the most good matches doesn't provide exact segment information. Everyone knows this is AncestryDNA. What I have managed to do is reconfirm, over and over, that I am indeed related by blood to several paper trail ancestors.
23andMe isn't much better. They have a great chromosome browser, and now they have a great common match feature, but they don't have a way to post a tree at their site. No trees means not much progress using their site. I have, however, been able to collect some segments for my DNA mapping, which sure beats AncestryDNA. Family Tree DNA is a bust now too, because they have failed to attract enough testers. I haven't gotten a good match with them in a long time. I have in the past been able to collect some important segment data. Now that Ancestry is dominating the market for DNA testing Family Tree DNA seems to have had a steep decline in the number of testers.
Everyone says just ask your AncestryDNA matches to compare at GEDmatch. I have not been lucky enough to have many agree. My top matches, generally, have not to date agreed to upload to GEDmatch. Without being able to map my chromosomes with large segments from 2nd to 3rd cousins it's impossible to confirm where the smaller segments come from. I could put together a great chromosome map if only AncestryDNA somehow provided a chromosome browser. I would love to resolve a brickwall on my Campbell line using autosomal DNA, but can't without a chromosome map. Establishing exactly which segments relate to which families is critical to success with autosomal DNA. This can't always be done if, for instance, you are from an endogamous population. I do have ancestors who were French Canadian. This population is very interrelated. The French Canadian segments are useful anyway. They tell me these segments came from my maternal Great-Great Grandfather. Aside from the French Canadian line my family isn't endogamous.
Recently I'm noticing some matches sharing substantial amounts of DNA at AncestryDNA, such a 91 cM share. I know exactly how we are related since the match has a tree posted. I'm hoping that this match agrees to upload to GEDmatch. This alone won't be very helpful, however, without many more matches also sharing their segment information. It's the aggregate segment data that is so powerful when it comes to using autosomal. AncestryDNA cites the danger of matches discovering inherited disease information about a match through segment data as the reason they will not provide exact segment info. I'm afraid without the exact segment information the test isn't very useful for genealogists.
AncestryDNA really painted themselves into a corner by not providing the ability to share segments early on. They've decided to ignore this important tool and provide New Ancestor Discoveries and Circles. I've written in my blog about how a 4th cousin and I shared some of the same NAD's. This line has a brickwall too, so I was very interested in the origins of the NAD matches. I tried to workout how we were all possibly related. Those NAD's have now been removed by AncestryDNA. I guess we aren't likely related after all, or at least within the genealogical time frame. This waste of time could have been better spent mapping chromosomes.
I'll keep trying to persuade AncestryDNA matches to upload to GEDmatch. Otherwise I will remain at a standstill.