On Windows, with a numeric keypad, the following works.
Hold the alt key down, and then on the numeric keypad, type the 4 numbers listed below. Then release the alt key. This will insert the character in question. I keep a cheat sheet in front of me while typing, and have memorized most of the ‘chords’. But then again, I always was an emacs guy 
À 0192
à 0224
Á 0193
á 0225
à 0195
ã 0227
 0194
â 0226
É 0201
é 0233
Ê 0202
ê 0234
Í 0205
í 0237
Ó 0211
ó 0243
Ô 0212
ô 0244
Õ 0213
õ 0245
Ú 0218
ú 0250
Ç 0119
ç 0231
€ 0128
« 0171
» 0187
— 8212
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