Yes the technique is different. I'm sure you've read elsewhere that for the rear only brakes you stamp on the brakes at first and modulate the brake to limit lock up. The maximum weight on the brakes wheels (the rear) is as you start braking, after that weight transfers to the front and you have to modulate the brake to limit lock up.
A 4 wheel braking system like a KZ is different in that as you brake more weight is transfered to the front, where your most powerful brakes are. So you can in fact press on the brake harder and harder and harder until you reach the limit of the tires grip, which is increased due to the weight transfer.
So short answer, brake, then brake harder.
As for the trail braking issue, i'm having trouble understanding the comment
Could you expand on this? I don't know if you mean the outside wheel locks? Which actually makes sense with a kart because you unload the outside front wheel on turn in.
For any vehicle, the tires have a limited amount of grip that you can use. Braking uses some of this grip and so does turning. So in its simplest form you need to release the brake at the rate you turning the steering wheel. Like so.
How trail braking in its simplest form doesn't take into account a racing line change. If you've come straight from a rear brake kart you tend to drive a wider entry line to when you have the benefit of gears and front brakes. For fronts braking you often want to take what i call the motorcycle racing line. If we take a hairpin as an example, we want to make the racing line look like a V and do all our turning on the apex, this gives you the maximum opportunity to use the brakes in a close to straight line. Rear brake only karts tend to drive a hairpin in a U shape. This is because they have limited power bad so need to maintain apex speed (to stay in the RPM). Geared karts don't have this limitation.
Taking the corner below, a geared kart should take the double apex line because they can brake much later and use the front brakes to the maximum in the extended straighter entry. A rear brake only kart will take the green line, they will be slower in, but have a higher apex speed. The red line is a non committal line lol.