>>7697310The Tamiya panel line is probably the best dark wash, and you can't go wrong with it, that's why I recommended it.
About the masking tape I would strongly recommend the hobby one. The classic hardware store one works, but there is nothing more frustrating than finishing a paint job only to find rough edges, paint slipping under it the tape or being rip out when you remove it. A single tape it's not expensive and it should last you long.