OK I looked at Smok
If you want to keep using that model (possibly a 510 compatible threading based on the atomizer style) or it could be whatever mystery model Apollo uses. Dunno.
Buy their blank cartomizers (or the blank cartridges if it is configured as a 3-piece with separate atomizer and cart). They sell blanks (though their price is high)
http://www.smokcigs.com/accessories-1/
Buy the juice elsewhere that offers PG/VG mixes and lower nicotine. I recommend no more than 20% VG for a cartomizer (i.e. 80PG/20VG). FreedomSmokeUSA Tobaccos section - all of the ones that are not specialties are available in any PG/VG and in 6mg which is lower than Smok's 10mg Low level. Buy more than one flavor. I don't care for their Marlboro alike. Read the comments on the tobaccos. if you are using atomizer with separate cartridge you could also look through the specialty tobaccos (only available in 50PG/50VG so they are thicker). Do not buy from the samples section - they are all 24mg! (and they may include a free sample - it would be too strong for your mom and too strong for me too)
If you are using cartridges, just drip eliquid into the stuffing until it looks damp, not a puddle. And with either cartridges or cartomizers be especially careful not to put one back on the battery if you think it might leak - auto batteries are pretty easy to damage or kill if juice gets in the hole in the threaded end of the battery - they are totally dependent on a drag sensor there.
Here is their section on refilling cartomizers (in Getting Started) but for me it is blank
How It Works
Below is how I fill the cartomizers I use on manual 510 and manual KR808D-1. Filling the Smok cartos may be similar
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How I fill a cartomizer (Vapor4Life for KR8 or Boge 510 for 510 which are all soft-cap w/ no inner seals and defined central air channel)
I use thin (20% or less VG) liquid or Vapor4Life WOW liquids, preferably clear liquids w/ no sediment
Filling a blank carto - I pop off the soft cap (unbent paperclip carefully in the mouth hole, not catching any wires or stuffing!). I hold some tissue against the threaded end hole. I tilt the carto and slowly drip 18 drops onto the inner wall of the carto so it slides down into the stuffing while I rotate the carto. Then I wait 15 seconds or so then I drip however many more drops the stuffing wants to soak up. Then I do clean-up. If it is leaking, I clean that up. Then I tilt the open end down into the tissue and puff hard a few times into the threaded end to clear any juice out of the central air channel (I want to see light through there). If it looks too wet above the stuffing, I gently touch a bit of tissue to the stuffing (otherwise that liquid will be gurgling or spitting in my mouth). Then since this was a fresh fill of a blank, I now let it settle. I lay the carto on different sides for 15-20 minutes. Then it should be ready to vape. If you use thicker juices than me, then you may need to let it settle longer.
As I am vaping - if the vapor gets a bit light or a bit dry or tastes bit off or the carto is getting unusually warm, I will take the carto off the battery, open it, add 6-8 drops or whatever it seems to want (I will either hold a bit of tissue against the threaded end hole just in case, or skimp on how many drops I add to make sure I avoid drips if I have no tissue). I check to make sure the threaded end is dry, give it a couple of puffs into the threaded end to make sure the air channel is clear, and continue to vape.
Note - it is easy for me to "open" my main cartos for adding juice because I replace the white end cap with a plastic or delrin drip tip (I get them at LiteCigUSA.net). So I can easily pull that out with my fingers when I add juice and it keeps my lips cool if the carto is hot.
Note2 - If you use auto batteries, at the step where I blow through the central air channel (assuming you have one), you could stick a soft bit of tissue in the open end, touching the stuffing, THEN tilt the open and down and puff into the thread end. That will catch all loose juice in the tissue. It will not be the most filled carto but it will be the least likely to leak.