In my experience the cats will usually be leaving a trail of moribund fleas for the couple of days after treatment.
The problem then is the ones left in the environment waiting to hatch, but a treatment of Indorex and a bit of vigorous hoovering (which encourages them to hatch out) should do the job.
Do not spray your beds or clothes, just carpets/floors and vacuum/hotwash everything else. A friend of my mum’s got kidney failure after spraying all her clothes. Admittedly in the 90s so possibly not the same stuff but still, it is pesticide.
In my experience the cats will usually be leaving a trail of moribund fleas for the couple of days after treatment.
The problem then is the ones left in the environment waiting to hatch, but a treatment of Indorex and a bit of vigorous hoovering (which encourages them to hatch out) should do the job.