Solomon/Elenco/Velleman/Duratool...

[vindicator]

Just posting a new topic based off of my previous reply to a different topic.
(newb-alert)

My purchase order from 7 years ago says I have a Velleman (VTSS20U), while the manual says Duratool (ZD-929C).
I have been informed that these are cheap clones of Solomon or Elenco. But if they look the same too, one surely is a knockoff of the other.

Tips:
There doesn't seem to be any standard for tips outside of the end of the tip itself.
Some tips look hollow while others appear to have a solid core. From other threads, it looks to be true.
I can see the value of both; Hollow will trap the heat inside (as opposed to the heating element being wrapped around the tip (external/hollow). On the other hand, solid tips are probably going to be able to have more of a stable temperature.

Then you have varying lengths for the shaft of the tip. I'm going to guess that the inner/outer diameter is going to be different as well, but not sure if it based only on the heating element (40w iron vs 70w).
And what is the shiny exterior vs the gritty/coarse (ceramic? galvanized?) coat?

Compatible Replacements?:
If I'm looking at buying tips from where I bought the station, I'm seeing a $15 shipping fee on a $2 tip.
If I'm looking at Duratool, I'm seeing shipping overseas.
If I'm looking at Velleman, they are telling me it is not one of their products.
If I look at Solomon SL-30, they show tips below their station (821->827), but on the side link to tips from above which are 30T-??. (http://a1parts.com/solomon/index.html#Soldering Tips for)
If I look at Elenco SL-30A, they say their tips are NOT compatible with Solomon (http://www.elenco.com/product/productdetails/soldering=OTk=/solder_tip_for_sl10a--sl30a..1--8"=MzA=). It does however say it's compatible with ZD931, but while that may be close to my (supposed) ZD939C, it doesn't explicitly say it's compatible.

I'm just frozen in place not knowing where to move. My needs are NOT great. I may solder a few times a year, but it's likely to be even longer than that.
My current need is trying to desolder a component from my induction cooktop, but the solder doesn't melt at all. I can roll my tip in a molten ball of solder, but the solder on the board doesn't do anything (almost like it's steel or something).