Welcome to FC! There are numerous threads where you can find all sorts of information and opinions on what you're trying to do.
ISO abbreviates isopropyl alcohol (rubbing alcohol). It's a bit more toxic than ethyl alcohol (Everclear). Haven't used it for extraction.
This time I did a 10 minute quick wash.
1/2 oz bud (60g)
Decarb at 100C for 40 mins
Quick 10 min wash in 95% iso
Filter through coffee filter paper
evaporated 3/4 of alcohol
added 20ml of ready made vape juice
evaporated remaining alcohol.
Got a few brown powdery particles in the oil (should i remove this?)
Getting no noticeable hit after 20 or 30 draws
Have I added too much oil for 1/2 oz bud?
Any other suggestions please. Just about to try again but its an expensive mistake.
There's no need to decarb your bud for vaping. If you're careful with temps, you can retain terps for flavor and effects. If you want to decarb, for some reason, it's better to decarb the oil rather than the bud. That way, you get a complete purge at the same time, with better flavor, IMO.
Three minutes in the freezer works great. It's called QWET for quick wash ethanol. Any longer than that will start to pick up chlorophyll. Ten minutes at room temp will pick up
a lot of chlorophyll, and probably even less desirable constituents. The wash should be faintly straw-colored, almost clear. No green.
Vacuum filtration is a step up, but coffee filters are fine at first.
What you attempted can be described as solvent transfer. Tried it early on. (Actually made some tasty nic juice from bourbon. Need to try that again.) The goal was mainly to get concentrate to dissolve in vegetable glycerin (VG), which is nearly impossible. You don't mention whether you're using 100% propylene glycol (PG) or some mix with VG.
Any VG will ruin it, IME. It will be fine up to a point, and then the oil will precipitate out, messily. 100% PG
might work.
@randomtoker posted a method for relatively dilute PG, but don't recall if it involved solvent transfer. In any case, solvent transfer was tried and discussed in that thread. Worth a read and maybe a try.
No idea what you mean by "add too much oil for 1/2 oz bud".
Is there a problem vaping traces of this stuff?
It's certainly not safe. The answer depends on your tolerance for risk. One problem is, not sure how much ethanol will be left. How do you know when to stop the transfer? Some nic juice flavors are dissolved in ethanol, so there's relevant exposure. Best to let these steep before use to give the ethanol even more time to evaporate. If you don't, you can feel some irritation upon inhalation. Steeping would probably be a good idea, if you pursue this.
Be prepared to make expensive mistakes. It's not easy to get good, consistent results, especially without PEG. Expect oil from a ten minute wash to taste terrible. Sadly, don't know how to salvage this, especially if there's nicotine in the mix.
Advise working on your QWET technique, maybe set up vacuum purging if you want to retain terps. Dab the concentrate at a low temp, and then decide if you want to risk making e-juice out of it.