There are two ways that I used to do the pinholes. 1. Get a small tube of body filler putty and just put a dab on your finger and work it into the hole, dries in minutes to sand. If you can get a can of HIGH BUILD primer you can also use that. Spraying with the high build will cover and scratches, pinholes etc.
Out taking my time cutting mat to glass the engine well in. Getting horsefly bites too much. Will have lunch. Don't think I'll be back to it today. Too hot to be dressed in long pants and long sleeve shirts!
Did drill a 1" hole for a 3/4" drain tube. Nice and low!