Really the only technique is making sure all the DMT vapes off of the machine-ball. It is possible if your ball is too large that there could be some DMT flowing to the middle and just never getting hot enough. As for the bottle: Condensation is a non-issue as far as I can see as I show in this post

I just ordered some earth-silicate superwool from this site and so did amor-fati. I hope that it might be better at swabbing up that goo cause the copper definitely doesn't do the super well.

If you are using a bottle with a large neck then you might be wise to put the lid, if it metal, if not then fashion something metal, and put a dime-size or less hole in it for the kidney-bean size or less copper which will heat more evenly.

Lots of suggestions, pick and choose which ones you like