I had the same problem. I think I figured it how, after trying different way of mixing. There's no special sweetener needed, all you need is just Sucralose. If you want sweeteness forget about a gunked up coil. As long as it's crazy sweet right?
Here is the logic that works to make your ejuice a toothache sweet using just sucralose. Imagine that you have a plain snow cone, and you put some sweet topings on it. When you eat that plain snow cone with its toping the overall taste won't be pronouncely sweet. Why? because the snow cone is plain. The sweet topings don't provide enough sweeteness for the overall taste. Even you have 10% sucralose for your topings, it won't over power your plain snow cone.
Now, imagine again, if you have very sweet snow cone with plain taste topings. When you eat them, the overall taste becomes sweet.
So to answer the search for the like-the-store-bought sweetness is to where you add your sweetener. From my experience, before I mix a bottle of ejuice, I prepare a bottle of a mix PG 50ml, VG 50ml and sucralose 15ml (PG and VG 43.5% each, sucralose 13%), close the bottle, shake the crap out of it, and keep it for a couple of days. This is the process when all the molecules bind together. Just like the sweet snow cone I mentioned earlier, the sweetener binds with the snow cone, and your sweet snow cone is your PG and VG base.
2 days later use this PG-VG-Sucralose base and mix it with your flavor that you like. Flavor is your topings. And after, done mixing, do whatever you like to age your ejuice. Shake it, crockpot, ultrasonic, breath, steep whatever! Do your usual. The good thing is the PG-VG-Sucralose base won't alter the taste of your flavor since the sucralose already binds together with the PG and VG.
From what I illustrate above, the mix is not going to end up for a 50:50 mix. It becomes kind of odd PG VG ratio. A 60ish PG and 40ish VG. Lol....but you can play around with eliquid calculator to find the right % of the PG-VG-Sucralose base prepared mix. It's not that hard. It's just some simple ratio calculation.