I use a bike pump. To top up a few PSI from normal slow leakage only takes like 50 pumps per tire. It's good exercise, and it really doesn't take as long as you would think. Maybe 10 or 15 minutes total. I keep it in the trunk in case I need it on the road. Inflating a completely flat tire would be a lot of work, but since I have no way of repairing a completely flat tire and I would just use the spare anyway, it doesn't matter.
If you get a compressor, make sure it puts out enough CFM. One time I used a little one (120V, 1-2gal tank, not a dinky 12V inflator) to top up some trailer tires that were 30 PSI low. It took me an hour to do all four tires. 200+ pumps with a bike pump only raised it like 10PSI on one tire, and there's no way I was going to do 2,400 pumps. By the time I realized how long the compressor was going to take, I was already too far into it to want to hitch up the trailer, drive to a gas station, fill up, and park it/unhitch. Plus a gas station pump might have taken just as long.
If you get a compressor, make sure it puts out enough CFM. One time I used a little one (120V, 1-2gal tank, not a dinky 12V inflator) to top up some trailer tires that were 30 PSI low. It took me an hour to do all four tires. 200+ pumps with a bike pump only raised it like 10PSI on one tire, and there's no way I was going to do 2,400 pumps. By the time I realized how long the compressor was going to take, I was already too far into it to want to hitch up the trailer, drive to a gas station, fill up, and park it/unhitch. Plus a gas station pump might have taken just as long.