Yes, just cast on maybe the number of stitches you have on your hat before the decreases, then knit several rows before you switch to the (4!) DPNs. Knit a few more rows to get the hang of them, then start the decreases. Also yes, you’ll sometimes have to shift stitches from one needle to another, in order to have stitches to knit together.
I find it works best to have my left-hand needle on top of the others, so I adjust as I get to the end of each needle.
Happy swatching!