Well the thing is I'm very methodical, so when I wanted to learn RNG, as all the basics tutorials are about DPPt I started learning on Diamond, then I read the HGSS RNG post on page 1 of this thread to see the differences between versions. But I know it can be a long process (even more if you dont have DPPt).
If it's just a matter of delay and you already understand the principles of RNGing, then you can try to play with pikatimer, with basics settings like 600 calibrated delay and 12 seconds, and try to check with irwin calls where you land with the Seed To Time results. You check if you got the right second (should be easy to fix that) then depending on what delay you hit you play with the Other delay box to tweak the delay until you reach your target. That's how I did it first time I tried on SS and it worked fine even without initial calibrating. But if I hadn't done it on Diamond in the first place I wouldn't have understood what's it's all about.