So I have a Fox float shock (a standard air shock) and I was wondering if I could use a regular tire pump or do I need a special shock pump to fill it back up? Also, are there side effects of using either one? It's a rear shock and low on air.
As far as physically attaching the thing, that's easy, any shrader pump should fit as long as the head is small enough to clear anything in the way.
I've used a minipump to fill forks in an emergency, but it's not easy.
Shocks run at much higher pressures though and I'm not sure you're going to be able to get high enough with most pumps. Some quick Googling says Fox Shocks have a max of 300PSI, that's a lot.
A cheap shock pump can be got for $15, just buy one. The right tool for the job is usually the best way to go.