You have 3 options:
1 ) For small sums under $1k you can go through paypal, epass or normal check. Anyways, everything over $500 is a good idea to use escrow.
2 ) For mid sums between $1k and $20k use escrow.
3 ) For larger than $20k sums you can just send someone from your company with the proper papers to their office and do all the paperwork and contracts in place. Just tell your account guy to prepare all the needed contracts. After it's done you can even send your secretary. Usually I take the travel and use it as vacations traveling. Sending a live person for decent sums of money grants you the opportunity to know the purchasing company and probably deal some partnership with them in a future business. After all, if they are willing to pay a big sum for a domain then it's more than clear that they are generating money and business, so it's a good chance for you to know them in person
