Use one of your RDA's to test the flavor on that way it is easy to yank the cotton and clean it between testings so you KNOW what you taste is the new batch not some mix of the old one.
In my case, everything that goes in the RDA gets mixed so what one juice actually tastes like in a fresh wick is mostly for academic interest only. Many of my flavors aren't that impressive alone but a fixed mix will never be as interesting or occasionally amazing as a constantly changing one. Issues such as varying persistence of different flavors can be manually corrected for, or when it gets too strong give a shot of unflavored. THIS, to me, is how DIY goes hand in hand with dripping. I mostly use old fave commercial juices in my little tanks (2-3 bottles/year).
As to making small amounts, funny my first order seemed like a lot of PG and VG to vape, but then I realized it was only about 3 ml per flavor I bought (the nic took 6 months to finish at my rate though). Now that I have the gallons, 5-8 ml in a 10 ml bottle or 15 in a 30 is plenty small. I still don't make large batches even of stuff I use constantly, making it over and over allows for tweaking. I also will make single flavor mixes partially to get them steeping. Then these single flavors can be experimented with later, first mixing direct into RDA, sometimes remixing them into a little 10 ml glass "day bottle". You don't actively throw away much by that method, unlike a complex mix you know is beyond hope, although a growing number of bottles sit around orphaned until you finally clear them out (my numbered bottle sequence just hit #99).
