I've been using insulin (Eli Lilly's humalog) since before I ever used AAS. It was the first PED I ever used. Here in Canada it is OTC you just walk into the pharmacy and ask for it, I pay $32 for a 10ml vial, dirt cheap. I've never been denied but do get weird looks. As irresponsible as you'll say it is, in all these years I've never ever used a glucometer either.
My usual protocol is to dose twice per day, workout days only. Once first thing in the morning, then immediately post workout. 10iu both times. No more than 4 weeks of consecutive use followed by at least 4 weeks of no use while taking metformin.
Immediately following a dose I down a shake with:
110g dextrose
10g BCAA
10g creatine
15 minutes later I down 50g of whey protein. Then an hour later I get a proper meal in. I never go anywhere without a big box of Wonka Nerds candy. I got them in my place, my cars center console, and in my basement gym. Their main ingredient is dextrose and I just love nerd candies. They are always nearby.
I notice increased fullness in my muscles when using slin and it helps my strength break plateaus.
I recommend using metformin during the off time to improve insulin sensitivity. Everytime I get back on I make sure to start at 3iu and work back up to 10iu, basically to test my sensitivity in case I sonehow became hypersensitive while using metformin. I would not recommend jumping right back into 10iu following off time.
That's my experience, I actually just did a shot like 45 minutes ago.
Oh and I never, ever, do a shot if I intend to sleep sooner than 5 hours after taking the shot. If my workout happens late in the evening I just skip shooting slin.