And if anyone knows a way to strongly and successfully close a circle - any tips on that, please let me know. I'd like to start up summonings and rituals again.
So, there's two pieces here that I can see, one of which is on the surface about terminology, but might help a lot in how you go about doing things, and the other is about summonings and whether you might want to look at such things differently.
Opening and closing and which order they happen in: You talk about 'closing a circle' when you're done, but the way I was trained, what you're actually doing when you finish ritual is *opening* the circle you made at the beginning. I'm going to break this down more to avoid confusion.
In other words, the steps go:
1) Cast a circle, creating a ritual space suitable for what you want to do.
Usually some combination of one or more of the following: 'clean and prepared space', 'space with necessary elements for your work', 'defined space you can use as a container for magic before releasing it', 'space protected from outside influences and curious entities', 'creating time outside of time, space outside of space', etc.
Generally involves a mix of defining the space - some practices specify this as 'scribing' the circle, rather than casting, cleansing it or banishing unwanted stuff, blessing it or adding wanted stuff, etc.
2) Do the ritual you're doing.
3) Open the circle, by reversing steps that are necessary (thanking beings invited, then opening the circle back up to the normal flow of time and space).
So in this model the thing at the end of the ritual is restoring your connection to the physical world, realigning yourself with what's going on here and now, if you've done magical work, this is where it gets released on the physical plane, etc.
If you've been working from a model where you're doing the opposite - opening yourself to what's around you, without defined boundaries, and closing that up again after, that might explain some of the difficulties you're having.
(Also, in general, in my model, opening the circle is a lot less work and energy than setting it up in the first place, so if you are tired at the end of ritual/can't focus, it's usually a lot easier to manage.
There are even techniques - my trad refers to it as 'skyhooking' - for pulling a circle down deliberately but very rapidly, which can be done in a matter of a minute or two if you get to the end of ritual and have run out of all possible oomph.)
Summoning and other approachesThe other part is - ok, summoning specific people who are dead is not a thing I do in my practice because for me it falls somewhere between 'rude' and 'potentially really risky' and I don't see the point.
My tradition does a fair bit of work with ancestors, not just at Samhain (though especially then) but I was always trained to make it an invitation, not an insistence or summoning, because one of the risks you get when you say "You, here, now." (i.e. a summoning) is that either you don't get the being you intended, or you get them, and they're really annoyed.
If you go at it from "Hey, I'd like to spend time with you, learn a bit from your wisdom, and generally be around", and accept that (like invitations to living humans) sometimes they may show up, sometimes they may not, sometimes you get a different conversation than you were expecting, then there's a lot less possibility of a problem. (Sometimes I will do ancestor invitations with more direct purpose to them, but even then I usually leave a clear out.)
I think that's especially true if you're inviting people you don't know well and don't have much direct connection with (and in this case, don't even know if one of them is dead!) There's a 'what were you hoping to get from this ritual, and is there another way to do that' element here that might be worth looking at more closely.
In general, what I'd suggest is going back and looking at your ritual methods, making sure you know why you're doing each step, what it should accomplish, what might go wrong or weird with it, and then building up again. When I've taught people circle casting, and how I was taught, we've usually done a month or two just banishing unwanted energies from a space, a month or two banishing and blessing (adding wanted energies), a month or two scribing a circle, a month or two calling the guardians of the quarters, and then working up to inviting ancestors, deities, and other beings as relevant. Usually if there's something that's going wonky in your method or your ritual design, breaking it down into that kind of smaller piece will give you a good idea what's up.
For different ritual methods, I like Deborah Lipp's
The Elements of Ritual. There's tons of places where I disagree with specifics in that book, but I think she does a fabulous job breaking it down into smaller pieces, talking about how a thing at the start of your ritual method might affect the outcome, how to adapt rituals for different numbers of people or situations. You might find it really helpful for troubleshooting.