I wrote this some time back about how to adjust a hood.
Has the hood always been hard to open, or did it just recently become hard to open?
If it's always been hard, it is possible that at some point before you owned the car someone adjusted the pin or the hinges such that it's pressing against the fender lips and hence requiring the "slam".
If it just recently became difficult, did you recently do some adjustments to the hinges, the latch pin or accidentally hit something with the car? If so go back and double check what you did, the hood shouldn't need re-adjustment for most procedures you do to the car. If you smacked someone, then it's possible you've tweaked the hinges / hood and need to re-adjust.
Checking the manuals for how to align / adjust the hood, they give very generalized directions but don't address what you have.
I'll tell you how I did mine.
First do a visual, is the hood generally aligned to the opening? Is each side of the hood even all the way front to rear? Is the cowl edge of the hood even and about the same dimension as the side edges?
Now look from the side, is the hood at the same level as the fender edges? does it seem to be higher in the front than the rear or the other way around?
The correct placement is where the hood is separated from the fenders and the cowl with even spacing along all those edges. Additionally, the front of the hood and the rear of the hood should align to the side fenders on both sides of the car and not be above or below the fenders at either of these locations.
If the above is all correct, you need to adjust the Male Latch Pin. That's the one in the center of the hood and has a spring behind it.
If however you have a discrepancy on any of the above items, then you need to adjust the hinges, or the location of the hinges on the hood or fender.
To do that do the following:
Remove the Latch Pin and Spring Assy at the center of the Hood.
Mark along the edges of the hinges to the fenders and on the hood with a dark pencil so you can see where they WERE.
A visual inspection of the hood right now will also help, since the latch pin isn't pulling the hood out of it's "natural" fall.
If your hood is being stressed shut, you'll notice it here because the cowl edge of the hood won't be down at fender level. This is a good indication that the hinges have been mounted too low on the fender walls and should be adjusted slightly upwards.
If your hood had uneven edges on the SIDES, then you need to loosen the hinge to hood bolts and adjust the hood to the proper location and then retighten. Usually an uneven cowl edge line will also show up with uneven side gap, although a very subtle gap on the side will be more noticeable at the cowl.
If your hood is fine side to side, but is too close / far from the cowl, then loosen the bolts to the hood from the hinges, and carefully pull / push the hood till the gap is satisfactory.
If the hood is higher in front than in back or vice-versa, then you need to adjust the hinges to fender. To loosen these it's easiest to close the hood, and access the bolts from underneath the hood and behind the grill. You may have to loosen one or two of the bolts with the hood open, but you'll be setting the hood into position and tightening the bolts from behind the grill.
Move the hood / hinges up or down as necessary to get the hood to line up front to rear evenly with the fenders.
Once you've tightened the hinge bolts, then replace the latch pin, and tighten it enough that it doesn't float around, but loose enough that a good shove will move it into position.
Close the hood, and very carefully pull the cable release, and open the safety latch. This should move / force, the pin into the actual position required for the latch assy. Now tighten the pin.
Close the hood again, and verify that the Male Latch pin isn't pulling the hood too far down, or leaving it up above the cowl edge. At this time also check your Hood Height adjust screws on each edge of the cowl, they shouldn't be exerting pressure on the hood, other than that required to make sure it isn't fluttering on the edges and that the edge is even with the cowl.
That's it, hope it helps.