I use CIBT visa sevices. They have lots of phone help and great online forms (with excellent instructions) I do the crew visas with them since they give a dummy application, completed with the minimal answers required. Their fee is on top of consular fees and any other fees, like the proxy charge from Brasil consulate.
I sent my app/passport via fedex (we have 75% discount); CIBT offers a netx day label but it's $34 each way. BUT, if I use my label for return, they charge a handling fee, which is understandable. Oh yeah, many visa companies charge a percentage to prepay your fees, since they charge your card for the total bill.
All in all, an agency is worth the price, if you know their reputation and service prices.
I believe you can get the Cambodian visa when you're in BKK or similar, but Vietnam is done thru the consulates prior to departure.
When I did the Brasilian visas, I took the metro to the closest station, walked embassy row, then UPhill to the consulate--it was a PITA. I've decided IF I can do it in Atlanta, I will--if not, CIBT gets my $. I have a spouse/family account there, so, as our beloved/whacky exchange student from Recife used to say, "It's only MO NEE" (Rest is peace, Claudia! Saudade.)
Do lots of homework and don't worry about giving up the PP to a consulate.
Thanks D & K for the great information.
I am still trying to get the hubby to agree to a splurge trip and pay more than we usually do to travel - I have my list and he agrees to what I listed but he is still reluctant to use any of the savings to cover the costs ;-(
When I finally wear him down, then we will do some of the Cambodia, Vietnam, Africa, etc. packages on LL!