If you want to run PPS Sieve on CPU & GPU, you don't need the trick - just make sure you select the subproject and that CPU and the appropriate Nvidia/ATI GPU is allowed.
The other sieves are currently CPU only - just select them like normal.
When additional sieves get GPU support, the same tricks as for PPS Sieve can be used.
The only difficulty is that you can't choose which GPU subproject you want with this trick.
If you're happy to do CPU work too - again, just select the subproject and you're done.