I always used the acronym DEET to describe my approach to barefoot - Diet, Exercise, Environment and Trim. Then I realised that while this was all encompassing from an equine point of view, it missed a couple of human elements. These are Communication and Time; so now we have D.E.T.E.C.T.
If your trimmer is going to be any use at all then open, non judgemental Communication is incredibly important and if barefoot is going to work for you then you may need to be prepared to give it some Time.
One of the hardest parts of transition is not the taking off the shoes and conditioning the hooves. It's actually the transfer and ownership of responsibility. It can take Time for the understanding of what this means to be fully accepted and understood by the newly barefoot horse owner - I know it did for me.
With shoes most conversations about hooves start with something like 'My farrier says...' or 'My farrier always...' or 'My farrier can never keep a shoe on.' or 'My horse doesn't have thrush/LGL etc because my farrier has never mentioned it.' etc etc etc
So the responsibility for the health of the hooves seems to sit squarely in the farriers lap.
With barefoot, at least when its done the way I would recommend, the responsibility transfers very firmly into the owner's hands. It is after all the owner who is responsible for the day to day management of the horse, including Diet and Exercise which are two critical corner stones to successful barefoot.
Sore after trimming - Communication
If you read the forums (which I would only recommend you do so with extreme caution because there are some real nutters out there), then you will probably have learned that a horse should never step away from a barefoot trim sore.
In an ideal world this is true, but like everything there are exceptions.
Thrush - can make the back of the foot really painful and this is sometimes mistaken for navicular symptoms. The pain can be masked/minimised by lifting the back of the foot off the ground with an overly long wall (not a good idea). Or with tall bars, compacted/false sole or any mix of these.
So your trimmer comes along, spots the Thrush, points it out, recommends that you treat it. Maybe they fail to mention just how painful it can be, or maybe this slips by in general conversation and isn't fully remembered. Trimmer very responsibily deals with the overly long walls/tall bars whatever. But the result is the frog is back on the ground (where it should be) and now bears some weight. Which of course is painful because of the Thrush - so the horse will now be sore.
Low Grade Laminitis (LGL) - If your horse has LGL, it will probably have an inflammed solar corium. This is painful, but can be masked, until such time as the horse is trimmed. Again it takes clear Communication LGL and seek a way to resolve it.
Other weakness - Sometimes a horse can have a weakness above the hoof, which might not have been identified or its significance realised. This mare had one front limb a bit shorter than the other because of an accident. The hoof on that foot grew taller than the one on the other side. If you tried to trim the tall foot to the 'correct' length it made her lame. It took experience and knowledge to do a good job on her feet.
Or if the hooves have been imbalanced for a long time, the body above them may have invoked some compensations to cope. When the hooves are then properly balanced the body will need Time to adapt.
Sick hooves - Time
I'm often asked how long 'transition takes. Well that all depends..... Not just on how healthy the hooves are to start with, but also how much effort the owner is prepared to make.
But a high proportion of transitions to barefoot occur because the hooves are unhealthy and the owner is getting desperate and/or the hooves fail to hold a shoe. It took Time for the hooves to get to this state, and it will take Time to get them healthy again. The key usually being an appropriate Diet and Exercise.