Yes even those established investors are still using DCA method to invest in bitcoin. And DCA it is best approach for the long term investment. Oh yes, newbies can use DCA method to invest in bitcoin and it is will be very good for them when they have grown and understand the market because when they have understand the market their investment has grown higher. And that should be the outcome of the investment in the future because you invest it when you are newbie and when you grown, you investment has already matured.
As a newbie, they should budget how much should be using for the investment and not a random amount to invest monthly, but a specific amount is good for the the DCA.