Powdered bark is fine. I do not recommend the lazy man's tek, instead (if you want a specific tek) use Noman's.
Extractions can be fast, my friend can finish an extraction the same day he starts if he wants to. He hasn't noticed any effect in yield from waiting extra hours.
By reading a few teks you'll see the extraction process is really simple and can be simplified to a small number of steps.
My friend does extractions of 100g root bark, here's pretty much exactly what my friend follows every time;
1) Add 1 liter of water to a 1500 ml jar.
2) Add 100 grams of sodium hydroxide to the jar, close the lid and swirl it around so it all mixes in, let it cool down so that it is warm but not hot to touch.
3) Add 100 grams of MHRB to the jar, then shake it until it is all absorbed evenly, it will appear as black water.
4) Add 100 ml or more of naphtha solvent to the jar and close the lid, it will sit on top as a separate layer.
5) Swirl the jar occasionally for one hour, the naphtha should get absorbed into the mix then return to the top each time you agitate it.
6) After one hour, when the naphtha has returned to the top again; separate it from the jar with a pipette or turkey baster and squirt it into a glass dish. Be careful not to take any of the black MHRB mix.
7) Add 100 ml or more of naphtha solvent to the jar, close the lid, swirl for 5 minutes, then wait for the naphtha to separate to the top again, then pull the naphtha off with the pipette or turkey baster. Repeat this at least 3 more times.
8 ) Put the dish in a warm (~room temperature), well ventilated area and wait for it to evaporate (roughly 8 hours depending on the surface area exposure, the wider/flatter the better).
9) When the naphtha has evaporated you will be left with the DMT, it will appear crystalline.
My friend has found the acid step of teks to be completely useless, not affecting yield or spice quality so he doesn't waste time, material and money on what would be extra steps.
He uses powdered bark.
When the naphtha has almost completely evaporated you can add a fan to speed it up, generally takes about another 5 minutes when my friend does this and he doesn't find it degrades the DMT as it's only for the last few minutes to aid in drying.
For better yields, put each naphtha pull into its own dish to evaporate.
For safety, add the sodium hydroxide slowly, and alleviate the jar occasionally during the first few steps (to avoid the jar smashing from pressure build up).
Where eye protection, rubber gloves, be sensible, have vinegar ready to neutralize lye spillages and you should be fine.