Super cheap technique:
Tube, empty bottle/jar/jug, spanner, a cable tie and some Dot4.
Crack top off reservoir and remove rubber seal. Fill empty bottle with some Dot4 (new or waste), spanner on nipple, tube on nipple, other end of tube dunked in Dot4 in bottle. Then you get yourself in the rhythm: open nipple with spanner, squeeze brake lever, close nipple, release brake lever; open, squeeze, close, release; repeat until you see no more bubbles going into bottle. Then repeat for t'other caliper.
Throughout, watch your reservoir, never let fluid empty completely from it, keep topping it up. Secondly, ensure the tube end is always submerged below some fluid to prevent air flowing backwards into caliper.
Then just persist, last time I did this, I ran through about half litre of Dot4 until I got no more bubbles from either caliper. Finally, once both calipers are done and cleaned up, stick the cable tie on brake lever pulling it in. Leave it on overnight, can sometimes help the last stubborn tiny bubbles to slowly rise up to reservoir.