Smoktech single coils work great for me with DIY juice that is an actual 95% VG by volume.
There are a couple of ways I've done first-time fillings of cartos with high percentage VG. It takes a while for these viscous juices to soak into the carto filler if you drip fill. I don't like the condom method for filling. It wastes too much juice.
1. Syringe filling.
a. Learn the fill capacity of the carto. Smoktech XL is 1.7ml, for example.
b. Fill a syringe with that amount.
c. Fill the carto
d. Let the filled carto sit 15 minutes.
e. Blow out excess liquid from air passage.
f. Use the carto alone or with carto tank (preferred).
2. Drip filling. This method takes more time.
a. Drip three drops into carto turning the carto 1/3 turn for each drop (do this for all drip filling).
b. Give the carto a hard thermometer shake. This will force the thick liquid into the filler.
c. Repeat steps (a) and (b) for the first 12 to 20 drops.
d. After 12 to 20 drops are in the carto the thermometer shake will no longer be required. Continue drip filling allowing the liquid to soak in after every three drops.
e. After filling, let the carto set for 15 minutes.
f. Blow out excess liquid from air passage.
g. Use the carto alone or with carto tank (preferred).