While Finaject itself is no longer available, in some cases injectable preparations from Finaplix have been made. The substance is the same: trenbolone acetate.
Trenbolone is a steroid having the advantages of undergoing no adverse metabolism, not being affected by aromatase or 5alpha-reductase; of being very potent Class I steroid binding well to the androgen receptor; and having a short half life, probably no more than a day or two though I don't believe this has been measured. Fifty milligrams per day is a good dosing for someone on his first cycle or someone who is as yet less than, say, 20 pounds over his natural limit; while 100 mg/day may be preferred by the more advanced user who has already gained more than this. These doses are assuming that trenbolone is the only Class I steroid being use. There really is no need to stack another -- testosterone being the only sensible exception -- but if another is stacked then the amount of trenbolone may be reduced accordingly.
There is no evidence in the literature, nor I think practical evidence, that trenbolone acetate has a "special role" in burning fat. Rather, it is an extraordinarily potent AAS, being about three times as effective per milligram as testosterone esters. This seems to apply only to Class I activity, however. To obtain good anabolism from non-AR-mediated mechanisms, a Class II steroid such as Dianabol or Anadrol should be stacked.
There used to be a myth that trenbolone was "hard on the kidneys." I have found no indication in the scientific literature of particular kidney toxicity with trenbolone. I know a number of users, at doses of 50-100 mg/day, who have experienced no problems. It seems to me that the claims that have been made were from athletes stacking an incredible amount of drugs, and how the blame could have fairly been laid at trenbolone (actually at Parabolan, not trenbolone acetate) is not clear