Hello Trilby...Welcome...
I think, boiling it all down, it depends on the individual person and there drive, when we speak of DIY architecture...
I like workshop learning...when they are good and facilitated by someone with at least 10 to 15 years of design/build
experience and/or clear understanding of their own skill sets...I validate this as a teacher and workshop facilitator because...to me...to charge someone to teach them something...the teacher...should actually have some solid background in architecture well beyond just "liking something a lot" ...like cob. Which is where many of these "new teachers of workshops" come from, and often have less than 5 years of experience...Take timber framing...one of my specialties...I now have two "programs" I am following being taught and charged heavily for by folks that have only taken a few workshops themselves, have "NO" architectural background experience, or training at all...yet they feel... more than qualified to "charge and teach" others for what they "think they know." One of them actually being brought to my attention by a young (and very good) Cob facilitator himself, as these other "Cob instructors) are teaching some very questionable information...
All in all...be careful with all information, vet it well, and get second opinions...
Now on a very positive side of all this...is "self discovery" and/or learning with a group of "like minded" folks...I have seen some pretty remarkable workshops "sponsored by novice." Now this may seem paradoxical from my other statement above, however, in this situation we have a case of "experiential self discovery," and all participants are learning and teaching each other together by the "experience of the activity." I have seen some of these as "labor swaps" and others as "low cost" opportunities to help someone build their home while everyone learn and gain experience...All in all, if going to pay someone more than $300 for a workshop...I believe the facilitation should be done by an actual "expert" in the give field...in my view of it...
I have to second...strongly...understanding the "building regulations" for a given area!! Don't build without approval...it seldom ends well...
Next...plan to plan...and then...plan some more... This is kind'a like the old axiom..."measure ten times...cut once." I can't stress to folks enough..."good planning"... and modeling...even if they have to hire (or teach themselves) how to draw technical blueprints and/or CAD modeling... The structure that is going to be built needs to be built..."in the mind first"...then..."on paper or in the ether of zeros and ones..." Sculpted houses sound romantic and nifty...I haven't seen one yet that doesn't have challenges and are full of "I wish I had done that different or better" all through them...
As far as books...read them all...good, bad and ugly... Understanding the "complete picture" is vital, so reading different books (even some that may not be so good) will give you a complete spectrum of understanding a building modality...In this case Cob...
As for building a 2 story building...I recommend against it as a novice unless they have training in architecture, engineering and/or other building arts...(or the structure has been professional designed and is being guided by same in its construction.) I personally do not recommend to anyone "structural cob,"
straw bale or any other such building unless they are at the "exper level," and even then the will never be as strong or robust as a cob structure with a superstructure of timber. That is just my "prudent nature" as I see way more "bad to average builds" in this "natural building movement" than I see "excellent builds" when done by novice DIYers...Structural cob is not for the novice DIYer...in my view...
I will own my very subjective view on this next part (but can back it up with decades of observable and tangible experience)...cob is not easy or the easiest...natural building method when compared to other modalities...So if doing this because of a love of cob...go for it!!..However, if doing this for cost and ease of building? Well there are other choices out there just as good (I personally think better) than standard cob...Even a log
cabin and/or timber frame (if the building site or areas can yield timber) is "as easy" as cob. In Nevada, this is still a possibility as is "adobe block."
Good luck,
j