it is so funny how many different ways there are to do the same thing.
i have been on a face/monster slide kick lately and i have personally found it easiest to do all my attachments before i push the bowl.
i like to still have air pressure when i attach big solid horns as i use the blowtube to slightly blowout the connection between the horn and bowl. i like the look of it pulled out a bit,and it allows me to get the connection quicker with less heat time. that means less chance of messing up other parts with details.

when it comes to connecting the art to the ground joint. i have been leaving an extra 1/4 inch of length over the desired look to allow for condensing of the thin glass the joints come on.

i spot heat with a pinpoint flame and do opposite sides first. once i made it around the circle and know its is melted solid, i then make it a bit fluffier flame and gently heat the entire weld while constantly rotating.
pull out of flame and give a second or so before you puff ever so gently to even wall out.

from there i pop hole/ push bowl and put away in kiln.

as for the how to hold it. i use graphite glass joint tool and for the actual art that i am attaching, i use a hot sealed punty. i dont like working with grabbers for the time it takes to make all the work. just melt off the hot seal before the hole pop and go with it.

i am for sure no expert, but this works well for me.