It is a fiddly operation to be sure, but boresighting as described above can still be done quite effectively. Did it that way for years, always able to get onto a 8x11 sheet of paper at 50 yards and often at 100. Just gotta hold it perfectly still while doing so.
But I will point out that if you have a laser available, and it sounds like you do...you can boresight while standing up holding the rifle at your shoulder after drinking a pot of coffee and eating a box of Skittles. Step outside at dusk, install the laser and switch it on, project the laser dot onto something 50-ish yards away, look through the scope, and adjust the crosshair to intersect with the dot, or perhaps a bit above it (depends on the cartridge). Doesn't matter if both the dot and crosshairs are dancing all over the target; their relationship to one another will be fixed, changed only by your scope adjustments.
Lots of shooters like to pooh-pooh the lasers, much preferring to squint and sweat and swear as they peer down the barrel. Gets really ugly when they try to boresight a lever gun or something else that makes looking down the barrel problematic. I'm not a techie guy, not even close...but, for bore-sighting, lasers rock!