Most dyno systems use an O-berg-style oil filter. You can learn a lot about the health of your engine by checking the O-berg after the break-in session (excessive amounts of aluminum slivers can mean you're chewing up bearings or a piston), but it must be thoroughly cleaned of any residue from the previous engine before the dyno session begins.
When filling the engine with oil for the first time, Kevin Troutman prefers to pour a quart each over the rockers to make sure they have plenty of lubrication at startup. We're using Royal Purple's dedicated break-in oil because it is formulated specifically for flat tappet camshafts. Almost all off-the-shelf oils lack the zinc and phosphorus additives that are critical for protecting flat tappet cams because those materials can harm catalytic converters. An oil designed specifically for use with flat tappet race cams is critical to avoid a lobe failure during break-in.
Comp Cams also produces an excellent oil additive that we use with every new race engine. It also helps protect the flat tappet cam lobe and lifters during the break-in process when they are the most vulnerable.
Another advantage of going to a dyno is that a professional engine builder will have the equipment to properly prime the oiling system before starting the engine. Starting an engine "dry" the first time is OK if you have used plenty of assembly lube and the engine fires up right away. But you can't always guarantee that it will. When priming the oiling system, you should have the valve covers off to make sure oil is getting all the way to the rockers.
Although he had already checked the spring pressures when he assembled the cylinder heads for us, Kevin Troutman checks them again. You don't want the spring pressures to be too strong when breaking in a new engine with a flat tappet cam. Ideally, you want the spring pressures to be between 80 and 110 pounds on the seat and no more than 280 pounds at maximum valve lift. Too much spring pressure can wipe a cam lobe (or grind off the nose) during break-in, while too little seat pressure can keep the lifter and lobe from properly mating during the break-in process, which means the cam will possibly fail once you start making full dyno pulls. If the springs you plan to race with are too strong, your engine builder should be able to offer some break in valvesprings as part of the dyno program.
Another priority during the break-in process is getting the rings to seal up. To help this, you want to minimize crankcase pressure. During racing conditions we won't run a breather on the right side of the engine, but for break-in we vented this side too.