If smoke is harsh and tastes bitter then you might be burning it. Also previous poster asked if you had mesh pre-burned - to test if mesh gives the taste, simply try several inhalations of unloaded machine and see if there is any taste.
I've written post in the past, describing my method, but can't find it right now.
Basically you should consider the following:
0) For me torch works the best
1) Start drawing air very slow, don't aim fire directly at the mesh/spice at first. Hold your torch so that vector of a flame is roughly perpendicular to the bottle. When you draw air in through machine, torch flame kinda bends towards mesh as if being sucked in. Regulate your rate of inhalation to achieve this effect. This way you are vapourizing spice with hot air and avoid direct contact with the flame
2) At this point hot air (and not flames hitting mesh) should be flowing into the machine starting to vapourize spice
3) Control intensity of vapourization by playing with distance and angle
4) For 2nd and subsequential hits, you might want to start aiming torch flame directly on to the mesh to the point, that outer mesh layer becomes red hot. This is to get spice which escaped into the depths of your mesh
5) Hold bottle so that it points slightly down, not horizontal. This is because liquid spice runs from flame and if you hold it horizontally or upwards - you might get some run into the bottle.
Physical sensations - for me it's body load, increased heart rate, buzzing in the ears
Hope that helps
P.s. I just re-read this and it sounds complicated, but in reality it is pretty easy, also it sometimes works better if you have somebody to handle the torch for you, so you just focus on inhalation.