Ha, bei mir geht das genauso mit der Tierliebe … 😉

very,very helpfull..esp because i follow you’re work,and got a ton of ideas because of all you’re experiments 🙂
as far as english goes,in case i ask another question,please feel free to respond in you’re language,translators are amazing now days 😉
cheers

Bei echten Motten hört meine Tierliebe auch auf…und die Larven des Blütenkäfers werden auch, ohne mit der Wimper zu zucken, geplättet.

I rough the prefelt when it is thick and more felt like prefelt. So you get easier connection to the ground. Roughen is like to comb the ends of the fibres to the surface.
My experience: the more solid your prefelt, the more you have to roughen it.
I never roughen my thin prefelt for scarfs!
Hope my answer was helpful.
English answers always takes a little longer, but I try my best.