This page is kind of long, but stick with it because Tanya's site is the best for CKD, of which giving fluids is an integral part:
https://www.felinecrf.org/subcutaneous_fluids_tips.htm
I've given fluids regularly to 4 cats over the years. The 3 best just sit there like little angels. The 4th one was like Toasty. I had to burrito her in a towel, I sat on the floor with my back against the wall, and my legs stretched out straight with her nestled between them with light pressure. I think it also helped that I was in our smallest bathroom with the door shut. Much like giving insulin, it helps to acclimate -- go to that room, burrito him or whatever method you choose, give lots of praise, maybe some treats, and just let him go. Practice that a few times a day.
It sounds like you actually got the needle in, if that is when the kerfuffle started, had you warmed the fluids? That made a huge difference for the cat of ours that was like Toasty (the other 3 didn't care, so I just used room temp fluids for them).
If you got needles from the vet, then I am guessing that they gave you the 16 (or maybe 18) gauge harpoon needles. It's a delicate balance...the larger the needles, the faster the fluids flow and the quicker it is over with, and they probably gave you big ones. That might be the best for now because he isn't handling it well. BUT if Toasty is reacting at the time that the needle was inserted, then a smaller gauge needle (which actually has a BIGGER number, like 20 gauge), might help, but then the fluids go in slower and it takes longer.
Moral of the story, it might depend a little on when you think the problem starts. If Toasty just doesn't even like being restrained and/or still, then that is a different problem.
I'm sorry that I haven't followed Toasty's journey thus far, so I don't know if fluids are a short term or long term thing. If long term, then I assume it is for kidney disease, in which case I seriously do recommend that you spend time on Tanya's site. I think that Tanya's site is to kidney disease as FDMB is to feline diabetes. There are a lot of money saving tips there if you are doing this long term, or I can help with where I source everything as well. I can get an entire case of fluids (12 bags) for less than it cost me to get one "fluid therapy" kit (1 bag of fluids+10 needles+1 line set) from the vet. I do still need to buy needles and line sets in addition, but I can buy those cheap as well. I literally couldn't afford to keep our oldest girl on fluids regularly if I had to buy everything at the vet. I
love our vet, but they know that I have to save money on supplies like this, specifically so that I can save our money for their actual veterinary services.