With a bolt rifle I remove the bolt and look through the barrel. It is easy enough to adjust the scope and get within 2-3" of your aiming point at 50 yards with the 1st shot. I then adjust the scope again. I move straight to 100 yards for shot #2. It may not be perfectly zeroed but will once again be within 2-3". After some scope adjustment shot #3 should be close enough for a hunting rifle at 100 yards. After that I start shooting groups and may tweak the zero if needed before moving to 200 yards and repeating.
If you can't look through the barrel to get the rifle bore sighted then use a bigger target, one that you can't miss. You can start at 25, but I've never had any problems starting at 50 even when I couldn't bore sight. I save cardboard for this, but a sheet of poster board is less than $1. You can tape over bullet holes and use the same target multiple times for zeroing.
Remember, all you need to do is get one hole in the target. It doesn't matter if it is 2" or 2' from your aiming point you should be able to get the next shot near perfect zero.
I've never found any of the various tools used to sight a rifle to be any more accurate, save me a single round of ammo nor 1 minute of my time.
Most hunting scopes will move point of impact 1/4" at 100 yards with each click of adjustment. At 50 yards 1 click = 1/8" and at 25 yards 1/16". If you start shooting beyond 100 yards remember that at 200 yards each click is 1/2". At 400 yards 1". Some scopes are different so it's a good idea to check specs.
If I'm 3" low and 2" right with my 1st shot at 50 yards, then I need 24 clicks up and 16 clicks left to get the rifle perfectly zeroed. If shooting at 100 yards and off by the same distance, then 1/2 that number of clicks are needed.
If you're using a decent quality scope that accurately moves the POI with each click it doesn't take many shots to get zeroed. I like a target with 1" grids on it to help measure how far I'm off in each direction.
Another tip. If buying a new scope, it should be already centered. If the scope has been on another rifle, it probably isn't. To center the scope, turn the elevation dial as far up as it will go. Then move it as far down as it will go counting clicks as you go. Just to keep the math simple let's say you get 150 clicks total. If you move it back up 1/2 that (75 clicks) the crosshair is now centered vertically. Repeat for windage.
If you do that, you're less likely for the 1st shot to be WAAAY off.