If you are going to clean the head without a resurface, careful usage of a putty knife or razor blade scraper can do the job, but it is very easy to scratch the aluminum surface. I have on occasion used copper RTV on aluminim heads to fill minor gouges in the surface, spreading it very thin with a razor blade, just enough to fill the void, (or as a surface release layer when used with porous compound gaskets like felpros, but not on a Supra motor, as I can always find teflon coated metal-graphite laminate gastkets for them.)
The block is much less suseptible to gouging being almost the same hardness as a razor blade or putty knife, but the concerns are the same.
Most any kind of normal solvent can be used if you avoid getting solvent on your valve stem seals or other non-metal parts. Carb cleaner works good for this, even for the pistons, I would shy away from certain types of brake cleaners as they can cause cylinder walls to oxidize and develope a thin layer of rust before you get things back together.
If you resurface the head, you don't really need to do more than a loose cleaning as the machine shop will grind it all off and leave a smooth fresh surface.
You may want to go over your surfaces with a light sand paper or scotch brite, to scuff it up a bit to achieve a better gasket seal (a polished looking surface would almost be too smooth). Be sure none of this sanding debris gets into the cylinders.
I have always used rags in the cylinders to keep out debris, the idea is to remove the rags in a quick motion when finished to pull out any debris that fell in (slightly oily or greasey rags are actually good for this as debris will stick to the rags, and keep the walls from oxidizing.). The same can be done with oil and water jackets using corners of the rags. Use compressed air to get extra debris out of the cylinders, the most critical part. Small bits of debris that may still get in to the oil jackets can be filtered out of the oil through normal operation. Small debris in water jackets can be later flushed out of the cooling system, but rarley causes an issue.
When you re-assemble your enigne, start it up and run it up to normal temp, maybe drive around a little but not hard, then remember to re-torque your head bolts to spec after a couple of heating-cooling cycles. Change your oil and filter within a few days, and flush your cooling system. You are bound to have some bits of debris, and remnants of whatever was happening to the Oil or Cooling system before you fixed it. Don't let this scare you, it sometimes takes 2 complete changes/flushes to get it all out.
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