Hi and welcome to Purrs In Our Hearts,
I'm no expert but I'd be inclined to let him properly settle in for a few weeks, get used to your home and gradually get his bearings outside before introducing a second cat by that I'm not suggesting that you need wait months but at least until he has found his feet so as to speak. I know this means doing things twice around as you said but I think that it might be a bit hectic and less worrying than trying to keep an eye on them both at the same time. As I said I'm no expert although I have had outdoor cats and have done quite a few introductions over the years. IMHO there's no guarantee that introducing a new cat will go more smoothly were you to get him a buddy straight away than if you waited a
short while as it depends so much on the cat/s' natures if anything I'd have thought that it might add to the confusion at a time when your new cat is getting his bearings. I do however think that two cats do make for excellent company for each other especially when one (me that is not one of the cats
) is out at work. My experience is that it is easier to introduce a female cat to a male cat or vice versa than two males but then again it depends on how territorial and tolerant your first cat is and when I introduced Frankie to Alfie I took a few days off of work to be around in case fur started flying but I'm happy to say that it never did and Frankie just slotted into the scheme of things very well and they've become great mates but as all my cats are indoor cats as two of them have FIV I didn't have the added concern about them going out but that in turn means that one has the concern as to how are they going to get on together when they spend all their time in and around each other's company especially when one is at work.
I'm sure that you will get better advice here shortly.
Kind regards
Leigh
Oh and good on you for giving a home to a rescue cat
