Some of my most comfortable finds are a half to a full size larger than my foot but adjusted to fit using insoles and such. Those stick on heel grips never seem to stay in place for more than a couple of wearings though so the tongue pad is definitely the way to go.
This is only for thrift finds, however. Anything bought online or from other members need to be the right size AFAIC. Also, loafers have to fit right or they're a waste of money.
4 pairs of socks always works for me.
I was once told to put on clean socks every day, by the end of the week I couldn't get my shoes over them