I got the achieved a few weeks ago. What i did was: (If i recall correctly)
1. Start as leinster, what you need is a neutral or hostile england (80% of the time in my experience) domineering will warn you and make it really hard to expand.
2. Ally scotland and tyrone, fabricate on the irish minor i'm forgetting (4BT, southwest) and take mission for connaught, declare in the first month and call at least Tyrone in, you don't need Scotland, but it won't hurt either. Attack his 3 armies with your 3 armies, your Irish friend will join the fight. Annex connaught
3. Build 3-4 heavies (At least as much as Scotland), money is just a number. Fabricate on tyrone, they will most likely have allied scotland. Go to war with scotland and Tyrone, france won't get called in if you don't make them co-belligerent. Block the strait to Scotland, siege Tyrone. Hope to wipe their fleet, if not, make sure you know where they are. Keep blocking the strait while transporting a single regiment to western isles.
4. Lift the blockade of western isles and trap their armies there. Blockade again, siege scotland, take everything you can, take at least highlands or aberdeen for fabrication on Norway, disregard aggressive expansion, it doesn't matter.
5. Watch england closely. If cornwall breaks free: no CB them! you can fabricate on brittany from there and otherwise England will just grab it back, Cornwall never take any allies.
6. Watch Denmark closely, support Swedish indepence if you can, or don't support it and go to war for a claim (you should fabricate) on orkney. Don't take orkney, or do, but the important thing is to get foothold in Scandinavia. You can easily build a powerbase in Norway and even Novgorod if Muscovy is not too treating.
I realize this is chaotic, but it worked for me.
Other tips:
- Gain allies ASAP. Burgundy and France are great (you can only get either one) Denmark can be usefull, but be ready to discard if their unions break.
- If anyone weak becomes Emperor: FREE NETHERLANDS! just no CB the first and expand from there.
- Don't be afraid to No-CB.
- Brittany is golden as long as you're allied to france.
- Vassalize scotland ASAP after you're first truce is over. Build enough ships and you can handle France. If France is your ally, wait until they won't join.
- England didn't break in my game. At their lowest point in the first 30-40 years they still had 15K manpower and 35K troops.
- If England is weak at any point, strike, and remember to park your fleet in the harbor, England will destroy it anyway.
- All land is good land. When i finally took on England i had almost all of scandinavia, the Hansa (Ohh the money from that lubeck node) and the Netherlands. Coalitions mostly form out of small countries, declare on one, siege quickly and you have 100% WS, so you can demand whatever you want and the truce destroys the coalition.