I use 2 table spoons per 4 oz as my "standard".
Go ahead and use your mom's good silver. When she starts getting all over you just tell her that Tom said it was ok.
Finally played around with some hda today. I used that ratio and the finished product was tacky even after the bait firmed up. Kicked it up to 6 oz plastisol and it works better. Also seems like plastic doesn't flow as well at lower temps. Definitely takes some experimenting. Damn cold out there now, will be a week before I can play again.