Nothing wrong with asking.
From my experience as an independent no budget, micro budget, whatever budget they are being called these days filmmaker, highly skilled technical jobs are rarely if ever done on screen credit. I have gotten many many things contributed to my films but when it comes to special effects it always comes down to some hard cash. The reason is unless you want your hopeful friend to do it poorly for free there is little option. Because if you want an effect for a film it has to be done well to look right and that always costs something.
Why? Because it is a highly skilled job. It required the skill of a specialist well trained in the traditional arts and then specifically trained in the area of SPFX. And there is no more highly skilled job than that of a 3D artist.
In fact, on my first film. I actually did sell the SPFX for a screen credit to a desperate start up company. I was extremely lucky. However by the time post production came around, the company folded. I was forced to rewrite and rethink the film. And the irony of ironies is that this is why I am a 3D artist today. The only way to do it was to pick up a copy of a 3D program, learn it from scratch and do the effects myself. At that time (1994) it was either 10 grand for the set up to do it alone or over 100 grand to pay to get it done.
I’d say it would be a good idea to go back and add some special effects to your budget. I would give it a range of about 500-1500 US depending on how much animation you want and how many shots.
The alternative is that it would be a much better sell to a student looking for experience. Try your local universities and art schools.
Or simply don’t write special effects into your films when you are doing it at this level. You have to be realistic.
Not that it can not happen, but it really is a rarity around here. Perhaps reword your request to something along the lines of a student looking for some experience.
I have never seen screen credit impress a craftsmen. Maybe some makeup artists coming out of school. But even they want a per diem for make up costs.
In a town away from Hollywood such as yours people love to jump in and help on a movie. It is fun for them and away from all of the jaded people in LA. But even far away from it all - I have done it - you won’t get craftsmen for free or very very rarely so. I did get a grave stone egraved as a favor once, but that was pretty incredible and I owe it to the charm of my co-producer.
Just my experience. Take it for what it is worth and good luck.