I have been lapping in engines for over 10 years and have won many championships/ races with them, It all started back in the 235mm days when novarossi supplied us very tight engines that were locking up during run in process. They recommended to "loose up with paste".
You can use the old hand tequnique or I use jigs and slow speed hand held devices to speed up the process. I always lap my personel engines 100% so as they can be turned over by hand when assembled. This has many benefits-
- no run in required race tune engine within 1 tank
- rod and bearings are still brand new and last much longer
- the polish in the bore is much more pronnounced hence the seal lasts about twice as long as normally run in engines.

Definately a very fiddly time consuming process but very worth wile.
Saying that let me warn you in my travels I have destroyed half a dozen liners perfecting this procedure.

Regards
KicKass