I'm actually doing this exact thing right now. I personally mix the Finacea with the AHA+ because applying the Finacea alone is kind of difficult, since it goes on dry and absorbs really fast. I found myself over-applying it, as a result, and in the end it leaves the skin dry and slightly cakey due to its creamy texture (even though it's marketed as a gel). I've done a lot of research online and found that people are much happier when they mix it in with their moisturizer and it still produces great results because you really only need a bit of it to work its magic.
After doing much reading, I reasoned that since I've moisturized with the AHA+ before and found that it works wonders on flakiness, helps with sebaceous filaments, and overall skin texture, why not mix it with the Finacea?
My assessment? It works pretty damn good, son. The active ingredient in Finacea -- azaleic acid -- is itself an AHA and I believe it can work effectively in tandem with the glycolic acid in Dan's formulation. I found that they compliment one another in that I prefer mixing the two rather than using either one by itself. AHA+ alone leaves the skin kinda greasy-looking and sticky, while the Finacea goes on dry, as I previously mentioned. Together, they appear to reach a happy medium and I like it a lot.
Some people may think that the combination is too intense, but I found that my skin has absolutely no problems with alpha hydroxy acids in general. If you can tolerate either one by itself, there should be no problems when used together. I actually found the Finacea to produce more itchy sensations when used alone than when it's mixed in with the AHA+. Having said that, skin and skin reactions are different, so listen to your epidermis. I personally can't stand things like BP and tea tree oil, but this works wonderfully.