I have 2 questions for any one who can help,

1- My building instructions require that I mix epoxy with Microbaloons to make a fillet , no mention of how much or in what ratio ? Why do you need microbaloons ?

2- When thinning epoxy to brush a firewall or inside of a cowl can I mix in some black paint to give the mixture the colour I need ? if yes will any paint do ? Or must one paint first and add the brushed epoxy later. Thank you.