A trick I use as a GM is to use opposition Dice pools. Basically I decide what Threat/Professional rating I want the bad guys to be just give them Dice pools for Primary functions at rating x3 and secondary functions at Rx2 and defaults/random stuff at rating or rating -1.
So example lets say we have the runners run into some corp sec. Well if its just plain old corp sec I generally peg them as Rating 3 and maybe the Sergeant at rating 4.
This means for things they should be good at like shooting their gun, swinging stun batons etc. they have a dice pool or R3 x 3 = 9 dice.
Things they should know how to do like Perception and running they will get R3 x2 = 6 Dice.
Thing they might know how to do R3 = 3 Dice or 2 Dice if I think they are defaulting.
Initiative I go with Rating x2 +1d6 for R3/4 +2d6 for R5/6 and temper with common sense i.e. the Rating 6 research scientist they are hostile extracting is not gonna have an initiative of 12+3d6 he does not fight for a living or even think he ever will so I would back him down to like 6+1d6
After that all you have to do is decide what equipment they have and its not too hard to figure things out from there.
I only actually spend time building Big bads and recurring opponents like the Knight Errant detective that is hunting them and stuff like that.
