I will attemt to answer some of the questions,
Pre vac always, post vac well this is infact an essential part of the procedure when encapping, how ever I do always ensure the customer knows the importance of the post vac stressing that the areas must be vacced the following day, and as a high percentage of my encap work is larger commercail jobs they tend to have in house cleaners who will do this task, I have yet to have a customer object to this although I dare say some c/c may say i should revisit to do this myself, Why ?I ask myself when most premisis will be havignthe carpets vaccumed as a matter of course .
Edges of carpeting as you will be aware do not have the amount of soiling as the rest of the carpet ,unless every body is walking with their feet along the eges constanly, and the brushes will infact create a covering up to edges if you are a skilled operator of the cimex
as for corners :
a good hand brush dipped in so;ution and a vigoures scrub does the trick, and stairs well I have even used this method succesfuly.
Greasy chinese carpet , never been a problem I clean 2 of their restraunts every 3 months , and once a year i extract with t/m and believe it or not , they still want me to encap instead of h/w/e .
Geoff