Pretty simple stuff really. To get milk Make a trap for wyvern using pillars 2-3 pillars high. Space out enough to fly pteranodon through and out pieces of ceiling on top. Out bohemoth gate on as well. Make this beside the scar can just leave gate open. Lure female wyvern( lowest level preferably) into trap get off ptera and shoot in head with trancs. After knocked out get milk from inventory (remember to bring preserving salt to lengthen life of milk) and then kill the wyvern works easily every time
To get eggs, however, take either ptera or another wyvern into scar but make plenty of cactus broth and feed it your mount as well as yourself and you can fly in scar unnoticed. Look for eggs once you grab an egg all the wyverns in area will come after you. Just fly through the scar until the wyvern un-Agro. Do not pull wyverns out of the scar. Pretty simple stuff
I got a level 150 lightning egg and I was so excited to hatch the egg...that when I went to put the egg down I accidentally ate it instead. :( ps4 users: R2 ISN'T GONNA DROP THE EGG YOU'RE GONNA EAT IT LIKE ANY OTHER EGG. REMEMBER THIS. LOGIC BEFORE EXCITMENT.