Small Gasket pieces fell into lifter valley

Keep the wire brush away from any internal part of the engine, use a sharp putty knife and take ypur time. The last thing you need are pieces of wire going into the oil pump and into a bearing if it doesn't jam the pump and break the stock intermediate shaft or spin the gear.

Paper gasket bits are least concerning to me.
However they will end up in the pick up screen if it's still intact, enough bits and it will clog it.
If you just have a couple bits, don't sweat it, just get what you can....and buy a magnetic oil pan drain plug ....just in case a wire went in.