thats how it goes. first time i felt every bone in my hand after filtering ~200mls tcyp220 in castor.
You feel it less as time goes on. also, heating it to around 50C helps a ton.
20ml syringes are a killer too. I moved to 10ML syringes, much easier to filter
Afaik, Castor has to either
1: be heated while filtering
2: have more BB to thin it, usually great for higher dosage blends. (think test D 550, Test C 300, though these do get thicker due to higher AAS content)
3 Be a MIG812/ castor blend
Ideally, for max comfort you do all 3.
any of these things make filtering more tolerable. I personally like it though, the high castor content makes it interesting for me/gives a reasonable amout of physical feedback, I usually filter while learning for Uni/ reading research papers. It does take hours for 200mls low BB/BA castor brews, but goddamn it keeps me in my seat learning.