Restoring Ch system

Hi all

I am fitting a new bathroom rad today and thought I might take the opportunity to put some restoring/ protection stuff in whilst I am at it. System is around 10years old and i have a system boiler (no header tank)

I bought some CalChem 3 in 1 a few weeks ago

When trying to find it this morning I found I also had some fernox restorer which I assume to be an old version of this product (not sure how old)

The fernox one says to put it in and run for at least an hour (older systems a week) and then flush.

The CalChem one says to put it in and leave it.

So my thinking was to out the fernox one in and leave it for a while (until the weather is a bit better and I can drain the entire system) drain it and then add the CalChem. Problem is the fernox is likely to be there a month.

So my questions

1. Is it worth doing both?
2. Anyone see any harm in leaving the fernox in longer?
3. They both say to drain, the entire system and then add to lowest rad to ensure it gets to all rads. Given the fernox is going to be there for some time thoughts on whether this is necessary?
4. Is all this agro worth it :)

Thanks

Lee.