GHRP-6, GHRP-2 and Hexarelin are all interchangeable. They are treated as interchangeable in the studies. They work via the same mode of action. Their slight differences are probably attributable to the different "batches" of non-pituitary neurons they excite. One peptide may excite one "batch" more or less than another.
Hexarelin is the strongest of the GHS peptides. It also induces higher amounts of cortisol & prolactin then the other peptides. It may (according to one comparison study) desensitize quicker. GHRP-2 is a little less strong with less impact on cortisol & prolactin. GHRP-6 has very little impact on cortisol & prolactin (although it is a little elevated above 1mcg/kg dosing) and is a little less stronger than GHRP-2.
So you could choose whichever is cheaper. I know GHRP-6 & GHRP-2 cost the same to make. However GHRP-6 at the moment at retail level is a lot cheaper...
There is no direct benefit to combining GHRPs because they all act through the same mode of action. You just choose one and run it from the saturation dose of 100mcg up to the maximally beneficial dose (which would be 300mcg - 400mcg) at each administration.
I know on the web you see old posts where people talk about the positive effect of combining Hex & GHRP-6. Thats just incorrect. What you do is make a decision on how much GHS you want to run and then choose among the GHS (GHRP-2, GHRP-6, Hexarelin, Ipamorelin). If you choose to use 300mcg you could use half (150mcg) of GHRP-2 and half GHRP-6 OR use Hexarelin , GHRP-2, GHRP-6 in equal thirds to fill that 300mcg dose slot.
However there is no synergy between these GHRPs and no advantage to dosing in total above 300 - 400mcg.
The GHRPs (GHRP-6, etc.) should ALWAYS be dosed at bed if you can (if you miss a dose no big deal). Depending on what study you read upto 85% of GH release in males occurs in that night-time (just after you fall asleep) pulse/spike. A dose of GHRP-6 of any amount will amplify that pulse which will give you more GH for the night. Looking at the study charts it appears that the pulse ends up being 2x to 6x higher than normal. Optimal dosage is 100mcg upto 300mcg - 400mcg. I've experimented with all doses and found 100mcg to be just fine BUT I do notice even deeper sleep at 200 & 300mcg dosing.
Keep in mind that glucose and fatty acids blunt (but don't eliminate) GHRPs induced GH release. The peak of the pulse occurs 30 minutes after dosing GHRPs so optimally take the dose on an empty stomach and wait 30 minutes before eating. This doesn't have to be exact...just the way to maxamize the pulse secretion. GHRPs can be analogized to a non-estered testosterone such as Test-suspension. You take it...you get the effect...then its gone.
CJC-1295 on the other hand is long-lasting. Most people are dosing it twice per week... That means no matter where you are or what you're doing throughout the week you have elevated levels of GH in your body. CJC-1295 can be analogized to a longer-estered testosterone such as enanthate.
Most are dosing it at 2mg per week split in two doses because that is what the CJC study in humans used (actually close to the mimimal dose of that study) and because these are bodybuilders tring to maxamize GH. But IF they used GHRP-6 a few times a day they could get an even higher amount of GH release or....
...if you are a 42 year old guy like me...and you understand that CJC-1295 = GHRH...and 100mcg of GHRH combined with 100-300mcg of GHRP-6 is hugely synergetic...and you are only trying to achieve a really good GH level then you experiment. It is now very well established throughout a body of research spanning more than a decade that includes more than thirty studies in humans that there is huge synergy in vivo between Growth hormone releasing hormone (GHRH) (of which CJC-1295 is a long-lasting analog) and Growth hormone releasing peptides (GHRP-6, GHRP-2, Hexarelin, Ipamorelin).
I experimented with just one dose of 100mcg CJC-1295 before bed...plus my 3x per day GHRP-6 dosing. I did this daily which meant 700mcg was used per week. That became my standard dosing scheme.
However, for the last three weeks I have been on an anabolic cycle (test, t3, slin) and wanted high GH levels. So my dosing protocol has been 100mcg CJC-1295 3x per day and GHRP-6 (100mcg-200mcg) dosed with it 3 x per day. That equates to 2100mcg of CJC-1295. I am finding this to amount to a high level of GH & to be hugely synergistic w/ the test & slin.
So my base level of GH stays elevated, IGF-1 stays elevated and when I add the GHRP-6 I induce a two hour amplified pulse of GH release which is great for growth. My dosing creates a pulse in the morning, post-work out and pre-bed.