As detailed in the other questions on the same topic, the correct response to spam is to flag it as such if you have the privileges. Downinvoting also helps but does not provide the additional information that a flag does. The StackExchange back-end picks up spam flags in particularly and will auto-block users after a threshold number of flags has been raised.
Note that even if a post is flagged very quickly by multiple people and thus auto-removed, this never reverses the fact that the something has happened. Thus a spam answer on a question will always bump the question up to the top of the front page. If the spam user gets destroyed (either by mod action or by the back-end) then this 'promotion' ends up being marked as dupe to the 'Community' user rather than a real person.
As TeX-sx is relatively small compared with the main site, there is something of a time lag between a spam post appearing and being removed. On the main site a question will get removed within a few minutes by user votes, whereas depending on the time of day it can take longer for us. If you feel the response to these things needs to be more rapid then you should raise the possibility of a moderator election: moderator votes are binding but of course depend on the number and location of moderators (all currently based in Europe).