I forgot to mention that you will most probably need a small forced air source at least to get the hunk of steel up to temp. and once at temp just pile on more charcoal over the top of it you should them be able to remove the forced air a common hand held hair dryer should be enough you don't need to try and make it bright cherry or near white hot since you probably are not going to re shape it.
Yeah I missed out on a 3 cubic foot heat treating oven a while back from a University of Texas A & M surplus auction, I had a bid in at $200.00 but in the last few minutes the price jumped over my max bid to end at well over $600.00 I can only buy at where I can afford things if they go over what I think I can afford even if they are still a good value I cannot justify spending more than I feel is within my means. Gone are the days when I would simply write the check then call the bank and say cover it for me I'll come in and sign the loan papers when I get a chance. I don't borrow so I don't have to worry about how to pay it back. I haven't bought anything on credit not even a credit card in 20 years. But I sure have accumulated a lot of stuff in the past 4 years