Hey ho, Chester. A bunch of us have done it that way. The standard ratio is to use a string of the hardener the same length as the one of putty you use and mix them together thoroughly. I found that I could get a little more work time (not much) by mixing a little less hardener in it. Don't mix up very much at one time. It sets up pretty fast! I haven't seen it in writing, but I think the color of the cap on the putty is what you're supposed to be aiming for. Like I said, I found it a little easier to go with less hardener than that. I never had any trouble with it not setting up doing it that way.
One suggestion that was made to me when I was doing it was to buy a tube of Bondo hardener from the auto store. I did that, it was pretty cheep. (If you're interested, I'll look up the exact name when I get home tonight.) It's red, rather than green, but the set up time seems to be much longer. I used it on only the last part of my Panther, so I really didn't have much experimentation with it. I don't think I mixed quite enough in as it really did take a long time to harden. I wasn't sure it was going to, but it eventually did.
One thing, make sure you clean your tools up as soon as you can after you finish. I found lacquer thinner to do a bang up job of cleaning them. (Be careful with it around anything plastic, though. Lacquer thinner will melt plastic in a heartbeat!
Good luck. Post more questions, if you have them. And keep us posted on your progress.
Bill
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DML M4A2 Red Army
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-- There is a fine line between "hobby" and "mental illness". (Author unknown)