I know it all seems confusing at first, but you are making this more complicated than it really is. For your purposes, unless the screen printer will be printing using the four color process method (screen printing photographs etc) onto the garments, create all of the items of your artwork as spot colors.. Do not use Process colors to color your artwork. The very first thing you should do in a brand-new illustrator file would be to clear out all of the swatches from your swatches panel. If you were designing art for a customer who wants the art work to be orange, purple, and green (for example) create 3 new spot channel swatches in your swatches panel. Spot color orange, spot color purple, spot color green

If your customer tells you he needs a specific Pantone Orange color or purple or whatever, then just add those Pantone colors to your swatches panel and color your artwork with those swatches.

I know it all seems confusing at first, but you are making this more complicated than it really is. For your purposes, unless the screen printer will be printing using the four color process method (screen printing photographs etc) onto the garments, create all of the items of your artwork as spot colors.. Do not use Process colors to color your artwork. The very first thing you should do in a brand-new illustrator file would be to clear out all of the swatches from your swatches panel. If you were designing art for a customer who wants the art work to be orange, purple, and green (for example) create 3 new spot channel swatches in your swatches panel. Spot color orange, spot color purple, spot color green

If your customer tells you he needs a specific Pantone Orange color or purple or whatever, then just add those Pantone colors to your swatches panel and color your artwork with those swatches.

Black is black and white is white. Do not worry about Pantone values for black or white. Just make the black artwork colored with a black spot color..