i am the proud owner of a remington 870 express and about the part with the slugs you cannot use slugs with a smooth bored barrel because then it would have the same range as just shot but a smooth barrel does have a corkscrew like design near the muzzle of the gun is because of the chokes and the reason why it has grooves on the slug was because it was meant for a slug barrel which has rifling in it along the whole length of the barrel and thus go increasingly farther. the slug barrel (wich you have to buy separately) costs about as much as the gun itself
And again, unless you are aiming at a target, DO NOT put you finger on the trigger of any modern firearm. Modern guns' triggers are better made to not need much pressure for them to fire. the downside with this is that you can accidentally shoot your buddy, or more importantly yourself, in da foot.
An infamous example of this is in Pulp Fiction, where John Travolta's character, , shoot the black kid Marvin from the opening in the head because he wasn't using proper trigger discipline.
Keep your finger on the trigger guard or on the frame.