Parts Full Orchestra

How would I write a piano reduction for my own composition?
I am in the process of writing a viola concerto, and am currently working on the orchestra parts. I will be playing this concerto at a recital by the end of this school year, which I plan to have around late May to early June. However, I won’t be able to have a full orchestra with me for the venue, but I still need something to accompany the solo part. Is the piano reduction mainly just most of the important lines in the orchestra parts put into one part, or is there some technique that one is supposed to follow?
Jeez, I hope you are doing this digitally, using Sibelius or Finale. Until this stuff came along, both my husband( really fine pianist) and me ( flutist – but really *functional* pianist) played a LOT of reductions for soloists in competitions, and they were often so poorly written, they would HURT you. If you have your concerto written in Sibelius or Finale, they both have apps that will write a reduction for you. They will both need tweaking, for sure, but at least the *bulk dump* (gee, that sounds gross when talking about art!) will be done.
If you do not own Sibelius or Finale, then you can get them, the FULL FEATURED ones, at a big discount at www.academicsuperstore.com. You will need to show your school ID, but will save a TON.m I cannot stress enough how much work this will SAVE you, even if now you have to enter your music that you have written so far. Good luck with your concerto!
BOHEMIAN RHAPSODY -FULL ORCHESTRA SCORE