I have also tried my hand at blending. It can be very fun and sort of mad-scientist-ish looking in the kitchen. Yes there were some that tasted about as good as my son's used gym socks but there were some real hits too. The key thing is to keep good notes and measure accurately. A digital kitchen scale really helped me with consistency.
I have also done the left-over blend. Heinz 57 and next was Heinz 58. Eventually I did run out and yes one of them was a fantastic bowl. It can't be made again alas, but it was still a beautiful smoke. It's like going to a restaurant you've never been to before. You have the best meal of your life. You don't go back for a while and when you do it's not there anymore. You can't have that meal again but you still had a heck of a meal before (and you wouldn't trade it). (substitute sex for meal at any point you see fitting).
I started out finding components or blends I found to my liking. I would mix enough for a bowl or two. Then I tried toasting and stoving different ones. I did some pressing as well (pressing heavy aromatics is a recipe for goop) and had some great results.
One problem you run into is the same problem my local tobacconist has with some of his store blends. If a supplier quits making something, goes out of business, changes hands, etc. you could run into a blend that is non-achievable any more.
Here's a blend I did a while back and need to do so again.
Major Nith Oriental (Nith is my joke for Not In The House)
4 Parts Red Virginia (Stoved for 14 hours / Air dried for 3 / stoved it myself)
2 Parts Black Cav
1 Part Latakia - Cyprian
1 Part Oriental (
http://www.4noggins.com/cornellanddiehlbulkturkishizmir.aspx
It has a slight citrus taste and goes great with a Pale Ale.
All this being said, it could just be that my taste buds don't work at all, my sinuses are obliterated and in reality everything I smoke smells like zombie's breath.