well, first of all you realy should read the effect list that you get with the kaos pas 2. each effect had his own coordinates and you are right, this need a little practice.
for example, effect no. 60 (BPM looper) has 4 fields where u can put ur finger, if u never worked with the kp2 this can be a bit unclear.
but you need for everything a bit practice? mixing requires also a bit practice too ;)

btw, did u also checked price/quality? the korg gives you more quality, effects for less price.
then we havent spoken yet about the sound quality of efx-500, i realy dont like that in every way (yes, ive tested it). the specs (sound quality) of the efx-1000 are better but price is way to high (and were are the new effects??).
max 300$ would be better...