[exim] smarthost + authentication configuration problem ..

hi,

where is the problem .. maybe only in my mind :/ exim 4.50 on linux
(it's debian, but no debian specific configuration, one large file used
and manualy edited to my conditions)

### router for remote deliver to providers smarthost
smarthost:
debug_print = "R: smarthost for $local_part@$domain"
driver = smarthost_smtp
domains = ! +local_domains
transport = remote_smtp_smarthost
route_list = * smtp.provider.com byname
host_find_failed = defer
same_domain_copy_routing = yes
no_more

### transport for smarthost plaintext login
smarthost_smtp:
debug_print = "T: remote_smtp for $local_part@$domain"
driver = smtp

where to place conditions or (which) options to put username, password
into this transport? if i use the standalone authenticators
configuration, how exim knows which of them to use? only by servername
in file /etc/***.clear?

in the routers i defined which transport to use, but in the transport i
define ?? nothing and exim knows what to use? i'm a little bit confused.