Method of attack for setting up something like an SRX 300 or ISR 1100 (GUI vs. CLI)

This is a bit of an embarrassing question but I really don't know how I would tackle this, any help to guide me would be much appreciated.

If I got handed right now something like an SRX300 or an ISR 1100, I don't think I could "from scratch" configure them from the CLI. I'm so used to the cheap and cheerful home routers, I believe I could do this easily from the GUI but there is a disconnect in my brain how I would learn everything I needed to know to fluently do this from the CLI.

I was thinking I would via the GUI first set it up and just reverse Engineer the configuration that results from that. I feel otherwise I might miss certain things or have to trawl through all the documentation having to skip over a lot of irrelevant stuff.

I think my issue here is that I'm so used to the commercial SME gear that I'm struggling to connect the dots for a blank slate Enterprise piece of kit. I also assume once I've done this exercise and really understood what is needed it would be easier for future times (e.g. just a lack of experience?)

Edit: Looking at the JunOS documentation for something like an SRX 110 or SRX 300 it appears like there is actually half decent guides on how to setup the device from scratch.

e.g. https://www.juniper.net/documentation/en_US/release-independent/junos/information-products/pathway-pages/hardware/srx110/srx110-index.html