First question: Is this the correct time to do a sodium carbonate wash?
Second question: Is this advisable, evap. instead of freeze?

If yes, he would like to then do a solvent wash ala Vovin tek.

This is something I have just recently developed. Even if you follow the tek above perfectly a small amount of basified solution will make it into your final result. This basified solution contains LYE which is extremely harsh to smoke. By doing this solvent wash after you have scrapped up the crystals you can virtually eliminate all of the lye in your final result as well as many other contaminants. Once you have scrapped up your result from step 8 place it in a small glass container. In another container place a small amount of Naptha and run hot water over it. You want the naptha to be warm to the touch.

Once this is done add about 50 ml of naptha to the flask holding the crystals. If this is not enough to dissolve all of the crystals then add a little more. The goal here is to put just enough naptha into the flask to dissolve the DMT but not too much because you want it to evap quickly. Stir the flask by swirling it around. Do not place anything in the flask as you will disturb the sediment that should build up on the bottom. If the crystals do not want to dissolve then place the flask in a pot of hot water ( heat bath ). This will make the basified junk gummy and it will loose form and sink to the bottom adhering to the bottom of the flask.

Allow the flask to sit for one minute. Then pour off the naptha. Once you have gotten all of the naptha add about 10 ml more to the flask and swirl it around. This is to make sure you have gotten all of the spice. You can then add this 10 ml to the other 50 ml making sure that no sediment from the bottom makes it over. If you feel you still may have DMT in the flask by all means add more naptha and attempt to dissolve it. There's no rule to how many times you can add naptha the sediment after being in the heat bath should be stuck to the bottom quite well. So use as much naptha as you feel is neccissary.

You can now evap off the naptha and re collect your crystals. They should be much cleaner and show a more defined crystaline structure.

If there is still junk you can do a second wash. You should loose very little DMT on each wash so do as many as you need to get a good final result.