Forward pressure only if inverted...
...or nearly so.
The reason forward pressure is taught is because a natural reaction is to pull back on the yoke if you're descending.
But if you're upside down and descending and you pull back, you'll point the nose straight at the ground.
Another thing to consider, the vortex sinks at a fairly constant rate (about 900fpm). You may not want to descend back into it for another encounter.
But if you pull back, your airspeed will deteriorate, placing you closer to the stall and degrade your control effectiveness.
Lots of things to consider. Every situation is different.
One thing you should always know before you follow a larger airplane is the wind direction.
If it's calm, you can expect nice stable vortices. If you have strong gusts, the vortices will break up and drift with the wind.
If you have a steady 10kt crosswind, the downwind vortex will travel downwind but the upwind vortex will remain stationary.
Of course the best advice is to avoid the wake altogether but sometimes we just get caught. In that case you have to make some very fast calculations and judgements.
There are no hard and fast rules--only good and bad judgement.
Fly safe.