Yeah, like rommel said, you need different wire.
Whatever shop sold you a mech mod & dual coil dripper with 28g wire doesn't know what their doing... kayfun, that's fine. With a dual coil dripper you will be nowhere close to a warm, full vape... let alone clouds.
You really need to be in the 0.4 (24g) or lower range with an atty that has good air flow like any of the ones rommel suggested to get into cloud production. The plume is a good atty and you can get it to produce clouds, but there are better choices now if seeking a fog machine.
I like a warm, not hot, medium throat hit so I build at 0.3 ohms. You will find out what resistance works best for you and your chosen atty.
If you are getting down into that low resistance you need a good 18650 battery. A 18350 of any kind is not safe in that range.
The shop was correct in giving you 28g for the battery's capability to keep you safe, but they were wrong if you are using a mech with a dual coil atty and looking for clouds.
I would look to VU for advice, not that shop. Know what you want before you go in... better yet... buy the hardware online and just pick up your juice from them.
I also agree, ditch the hammer... or keep it for a stealth kayfun nano 18350 setup.
I prefer stainless to copper especially with a hybrid connection, you really don't need copper unless you are getting into ridiculous low builds. And copper is much more maintenance.
Just a couple cheap suggestions...
copper
https://www.fasttech.com/products/0/10009268/1832004-xxix-style-copper-mechanical-mod
stainless
https://www.fasttech.com/products/0/10009631/1849003-surfrider-styled-18650-mechanical-mod