It helps to really move away from teh star like at the very least 10kls or more. I do it above or beyond the ecliptic plane, dont know if it helps.
Once far away, i just throttle down completely (30km/s) because signals pop up and dissapear immediately if you fly too fast
Last time i chased these it took me an hour to get one, then i got 3 high grade with isolators in em in a row. long, but easy to get.