In ARS Call Progress Tone Detection create a new plan, usually 1, Maximum Wait for A Tone to 1 seconds and Action on Time-out to Outpulse Default, don't fill in the Tones to Detect section and it will essentially act like a pause. Then in your Digit modification insert <T01> before anything else you might be inserting.
You can actually get fancy if you wish, say set Maximum Wait for A Tone to 3 seconds, and in Tones to Detect set to "NA Precise Dial Tone" (or whatever is appropriate for your location) and action to take to Outpulse Default, then insert that into your digit mod insert, the system will go off-hook and look for North American Precise Dialtone for up to 3 seconds, then start dialing as soon as dialtone is detected or after the 3 second time-out.
Help in this section goes along way, but using it is just inserting <Txx> including the brackets into ARS Digit Mod insert field.