I recommend HPLC purified although a little bit expensive.

If the dimethoxy trityl groups are left on the full length oligo then binding this to a column and washing away the shortmers that do not have DMT groups left on them is very good but as Aissa Saidi says the best method is HPLC which will eliminate all shortmers and failed sequences but base addition these days is very efficient and oligos can get quite long before HPLC or FPLC purification is needed

In my opinion PCR will the best option for you because it is accurate and cost effective