Switching substrates?

[Kinection]

My Petco finally ordered the Eco-complete and
I'm deciding on if I should start fresh by blasting my
gravel, so all the previous Turtle waste will be completely
be removed. (siphon'd 6 times, never got all of it out)
I'll let my new CRS settle in for about 1-2 more weeks since
I've already killed 2 through my mistakes. If I do this,
I'll lose a lot of beneficial bacteria, but I'll keep
the filter running the whole time. The shrimp will be
in a bucket for about 1-3 hours max.
If I do this, would this process be ok?
1. Blast/ clean tank
2. Add substrate (by cups, do I take the water in the bag too?)
3. Add water from bucket
4. Add shrimp?
If I do this, will there be any pH or spikes
that might kill the shrimp?