the ideal way is to add reverb to an aux track and mix to taste...and then bounce.
however, i'm not sure how your 1800 works. but you can do either way, whatever way sounds best to your ears. if you do a separate reverb for each track, it may be best to do the same reverb with the same reverb settings for each instrument. That way they all sound coherent. Putting a plate reverb on one guitar, a hall on another, a room on a third one...can sound kind of unnatural to some people. that's why using an aux track and bussing them all to the same aux track while keeping the dry track can give you more options. now you have TWO controls to work with...a dry and a wet.