First, unscrew the LPR all the way.
Turn the inline reg all the way in, so it's at it lowest setting. Don't lean on it, just until turn the adjuster until it's snug.
At this point, one of two things will happen:
You will be able to manually cycle the gun, and it will hold air, and shoot fine.
You will shoot once, and a bunch of air will come rushing out of the barrel.
The second is the most likely, with the reg set that low, so don't be shocked by it.
If you get it to shoot, and not leak, move to the next step. If it leaks, there's a few things you need to check.
First, make sure the IVG isn't cranked in all the way. Start with it 2 or 3 turns in from flush with the back of the body. That's just a starting point, you will have to adjust it later.
Second, turn out the inline adjuster until you can manually cycle the bolt and shoot air without it venting out of the barrel. Now that you have that taken care of, go to the next step.
Now, manually cycle the bolt to load a ball and cock the gun, then shoot paint while holding the bolt closed. With the LPR all the way down, the ball will push the bolt back, and give you low readings, so hold the back block tight to the body.
Turn the line reg up slightly after every shot until the gun is shooting something like a usable velocity.
At this point, there's no reason to sweet spot the inline if you can't even get the gun to cycle, so don't sweat that yet. You will 100% want to do it later though. There's an article at www.moodypb.com
if you're interested, as well as a few other articles you may find useful.
Once you have the inline set so that it's shooting somewhere near field speeds, remove all the paint, and slowly turn up the LPR until the gun cycles, and cocks reliably.
If you're blowing hoses before that point, there's something going on other than just the LPR/inline settings.
Even with old hose, if you cut off the stretched part at the end, you should be good to go. You might have the incorrect hose though, either a metric ID, or the old 90 duro stuff that was intended to be used with clamps, so replacing it is still a good idea.
Other issues can include timing (mostly pump arm, and cocking rod settings), LPR spiking, or creeping, inline reg lagging and dropping pressure, just to name a few.
Edit: Just to confirm, Dk is right. The BM reg is adjusted by unscrewing the adjuster in the bottom of the reg to increase the output pressure. The Rock is adjusted by screwing the knob on the end of it into the reg body to increase the output pressure.