Your rat will do fine with slin pins, use the .5cc (50 units) is preferable if you think you will experiment with the .5cc dosage. Usually it is done .25cc 2xED but .5cc 1x ED can also be run. Needle is usually 29 gauge, or 30 gauge. ½" is fine unless your rat is very fat. Intramuscular injection is often preferred, but subcutaneous is also effective.
Protocol is usually 5on/2off DAYS, making 10ml / month consumption. p-GH is available at two separate board sponsors, and their formulations differ somewhat, the more expensive one being said to be more effective but there is little feedback on it yet, as it is new.
Slin pins and alcohol swabs can usually be purchased at your local pharmacy. Ask for 50 unit with 29gauge needle and you'll seem to be a real diabetic.