Optiboot

Guide for AVRDragon, atmega328p, and optiboot bootloader.

gotchas:

wrong atmega328 (need atmega328p-pu, not atmega328-pu) (though this can still be used)
need fuse bits set separate from programming hex (pickit w/pics on the other hand handle this all in one)
need lock bits set
need 16MHz crystal when programming hex and lock bits (can use one from uno board)

set proper wiring on avr dragon (see image on right)

jumpers for breakouts on avr dragon. borrowed from elsewhere.

set fuse bits

avrdude -b 19200 -c dragon_isp -p m328p -v -e -U efuse:w:0xFD:m -U hfuse:w:0xDE:m -U lfuse:w:0xFF:m

add crystal (pins 9 and 10 on atmega328p, see datasheet) , load hex, and program lock fuse

avrdude -b 19200 -c dragon_isp -p m328p -v -e -U flash:w:hexfilename.hex -U lock:w:0x0F:m

hexfilename.hex - the optiboot loader is included in e.g. arduino-1.8.5/hardware/arduino/avr/bootloaders/optiboot_atmega328.hex

If everything is done correctly, you should now be able to upload from Arduino IDE.

use another Uno's crystal if you don't have one on hand. Solder wires and jump to dragon ziff socket.
efuse verifies as 0xFD, though some guides write 0x05. High bits are unused, so they are set to 1. Ends up as 0xFD if written with either 0xFD or 0x05.
atmega328 (not atmega328p), use -F with avrdragon.
board.txt somewhere in arduino folder also has proper fuse settings (search for uno)
first breakout on dragon is gnd/vcc header. Obviously, multiple of these can be used.