Remote,
Good choice!
Firstly, Caerlaverock WWT is a must visit. Tens of thousands of Barnacle Geese withe good numbers of Whooper Swan and the chance of rarer geese (Ross's, Snow, Lesser Canada etc.). There are also raptors including Hen Harrier, Deer and if you are very lucky Otter. Try an earlt start to watch trhe geese fly in from the Solway for an unforgetable experience.
The Merses (saltmarsh) nearby also hold Geese, waders, ducks and raptors, and there are Pink-footed Geese too.
Dumfries town centre is excellent for Goosander - try the weir, and last year had good numbers of Waxwing.
RSPB Mersehead is similar to Caerlaverock, but if anything wilder and more attractive.
Carsethorn and Southerness can be good for waders, sea-duck, divers and grebes, last year Southerness had Black Redstart and small numbers of Twite.
Inland the Lock Ken area is good for raptors including the re-introduced Red Kites, and White-fronted Geese can be seen around the lake. There is a kite feeding station and "REd Kite Trail" that I'm sure you wil be able to trace on t'Internet.
Further afield Loch Ryan beyond Stranraer had divers, gerebes, sea-duck (including King Eider last year) and white-winged gulls are regular.
I'm sure that there are more places that people will suggest- but these are just a sample and I am sure that you will find the area both beautiful and rewarding!