A question about switching salt

[Keri]

I'm in the process of setting up a 120 (still painfully waiting for the RODI to produce enought water) and I'd like to change salt brands. I still have more than half a bucket of red sea pro coral salt but I want to switch to instant ocean. I'm not so impressed with the RSPC that I feel it's worth the price difference between the IO and I see a lot of people with BEAUTIFUL tanks on here using the IO.
My question is: can I use the rest of the RSPC salt PLUS IO to get the 120 started and then continue to do water changes just using the IO?

Thanks for your input!