Driving a Ferrari the day after you get your license is bound to be tricky for anyone...
6v vaping is an art in an unto itself!
My suggestions: Get a nice tank to go with that nice tool. It's a lot of power to run into almost any carto.
Most likely, what HzG8rGrl said is spot on (paraphrased): "Whatever carto it is, regardless of the resistance, it is simply not wicking fast enough for that high voltage appliance"
It that is the case, no matter how you fill it, it is always gonna burn...
So, for now - until you find the carto, atty, or tank that works:
1. Soak it as best you can
2. Take short puffs (like 3 seconds max) and then let it set for as long as you can tolerate (1-3 minutes) while it re-wicks
3. Shop carto's, and maybe even tanks - I've heard good things about the dual coils from Smok Tech at high voltage.
Personally, I've used 1.7ohm Smok Tech Dual coils on a 5v appliance with no burning (never tried them at 6v! But several suppliers have them at higher resistance)
Now, that being said - personally, when I use the 510 and 808 mini carto's (I mostly only use Echo big cartos these days) I tried the condom bottom filling method and discovered HUGE variations depending on: Juice Thickness, Filler Type, and Carto Design. Like, sometimes it works, other times it hardly works at all...
If you get a thick liquid on a cart with a tight filler, and it will barely seep in with the condom method...
So, I'd bite the bullet and drip from the top... It's a nuisance on those tiny little carts, but we're only talking about a few days until something a little bigger arrives... The best way, if you don't have a syringe (first search youtube, there's tons of cool videos showing you how to do it), then - remove the cap (mouthpart), drip 5-7 drops allowing them to run down the metal into the edge of the filler, let it sit 20-30 minutes, then drip another 5-7 drops.
That's the way to manually fill a carto with a tight filler.
It's a pain in the ...., but it's pretty reliable... Then back to short puffs, let it rewick...
Pretty quickly, you're going to find a combination that let's you puff as much as you want, as often as you want, and not have to worry about filling so often... Just be patient, and have fun experimenting! It just gets better and better...
...and congratulations on your engagement! The gift of quit smoking is the best gift you can give!