should I use PropeciaFfinasteride after hair transplant due to shock loss on recipient and donor?

It is best to ask your surgeon about post operative care as each doctor has their unique regimen.  Taking Propecia after you had shock loss probably would not help. 

In my opinion, the reason to add finasteride is not for any short term benefit this soon after your FUT procedure.  Your apparent telogen effluvium post-operative shedding, should start resolving soon. Finasteride side effects are quite unusual, but taking a prescription medication indefinitely is not a comfortable decision for many young men, especially when it may affect them sexually. It is a long term approach & very effective, but may not show any substantial benefit for nearly a year in many of my patients. I hope this is helpful. Waiting for the results after HT is difficult, but almost always worth the wait for the patient.  Try to relax & continue the LLLT.  You should be close to turning the corner with obvious benefit you can actually see by about 4-6 months in the typical patient.

Finasteride works by blocking the effect of testosterone derived hormones on the hair follicles. Since the donor hairs from the back of the head are not influenced by these hormones, the finasteride won't have any effect on how well your transplanted hair stays or how the recipient site heals. However, it does affect the original hairs on the top and sides. If you are losing these, I strongly recommend you try finasteride for yourself. Not just for right after your transplant but as a general preventative moving forward. Side effects are fairly rare, and the nearly always go away quickly after you stop taking the medication.