Re: Motor has been sitting for 3 years.
WD40 is not a good lubricant. In fact if anything, it might do more harm than good.
You are correct it isn't a great lubricant, BUT the idea isn't for it to lubricate as much as it is to try to release the rings from the cylinder walls so they don't break.
Several of these ideas are good. My suggestions are as follows.
1. don't rush this process a day extra of sitting during it will only help not hurt.
2. pull spark plugs
3. take squirt can and squirt automatic transmission oil into cylinders, you can't use too much but you really don't need much either. Too much will just make a mess but that is the worst it will do. The idea of Autotrans (any auto trans fluid will do, Dextron II is likely you least expensive option) fluid is it is very high in detergant and is fantastic for unseizing metal components. Let it soak for a day at least, again longer is better.
4. take a johnson bar (swing bar) and put a socket on the crankshaft pulley bolt. Slowly move it back and forth not moving much in either direction. Idea here is to unseat rings from cylinder walls and move any debris from soaking on cylinder walls. Once you find it moves easily you can rotate the crankshaft a couple times around.
5. again shoot some trans fluid into cylinders let soak for a day, more if you wish
6. drain engine oil from oil pan and pour in new oil and change filter
7. pull distributor if you wish and prime oil system, this is an ideal step but if you wish can be stepped over.
8. with engine full of new oil and spark plugs still out crank engine over (rec disable ignition system so stray sparks don't give you a zap or ignite anything)
Recommend laying blanket over spark plug holes or rags to collect oil that will come out.
BE SURE TO STAY OUT OF LINE OF FIRE OF SPARK PLUG HOLES !!!! Trans fluid will be shooting out!!!!!
6. Once engine cranks over nicely 10 cranks/pumps you should repeat this step 2 or 3 times. No load is on rings or bearings and oil pressure has a chance to pump up a bit.
7. Now install new spark plugs and fire it up. Might smoke abit due to oil in cylinders but will cause no problems.
After running for 10 minutes making sure no abnormal noises, temp etc.... you can do a final step if you like and remove spark plugs and do a compression test to verify.
Hope his helps.