Well the easiest(but still very pretty) swirl i can think of would be in the pot swirl. Just decide how many colours you want , three being the minimum(imho) and nothing being the maximum. It sounds sort of complex now that i've typed it...but its a near impossible technique to screw up
Get your soap to a thin thin trace then split it up into however many colours you have, add the colours to each portion of batter. Say i'm doing five colours, i would put four of the colours into small containers or cups, and leave one colour in my main pot.
Then picture a clock, pick a colour and start pouring at 12 o'clock, 3 o'clock , 6 o'clock, 9 o'clock then whatever is left in the middle of the "clock". Then repeat with the rest of the colours, pouring where you poured the other colours, 12 , 3 , 6 ,9 , middle
Finally just take a spatula and give it a little swirl around the edge, then through the middle of the soap.
Winds up looking like this
View attachment 8693
I like to take any leftover batter i have, make some straight lines with it on the top, then swirl it side to side and then diagonally with a chopstick. Just the top layer.