JO BURG TO MAPUTO

hello everyone, i am an american citizen and will be flying into jo burg mid february and will go to maputo via bus. my questions are these? is it possible to arrange a visa to mozambique at the border? also, is it possible to bus into swaziland and get a mozambique visa there? if swaziland is a possibility, does anyone know how long the processing time is? btw, i am fluent in portuguese so i wont have a language problem at border.thanks so much in advance...:)