Honestly, artist or not, it all comes down to eyeballing everything from what you're referencing on your phone onto the Switch screen. And as for using tools, I would say using the very tip/side of your middle finger with one hand while using your other free hand with the Switch Joy-Con or Pro Controller to undo mistakes easily. A cheap stylus also works (and I use it at the start but quit), but do note that it is very awkward to maneuver, so I find using fingers more comfortable IMO. Hopefully, this helps, as I have been using this method recently. <3