D3 to D1 Pitching Transfer Advice

My son is a senior at a D3 school who will have 2 years eligibility remaining after this year (neither 2020 or 2021 counted due to COVID even though had full conference only season in 2021). His D3 conference is pretty good baseball. My son has been the game 1 starter since his sophomore year. He was voted by the coaches conference pitcher of the year his sophomore year and was all south region that same year. He had a good junior year, but had a couple rough outings in his junior year but still had 10 quality starts out of 13 outings. He has four pitches, FB, curveball, slider and changeup. His FB velocity sits in the low 90s but recently touched 94 and 95 mph during winter bullpen sessions off the mound. He is interested in transferring to a D1 program as a graduate transfer. He is in the transfer portal. Any suggestions on how best to get the attention of a D1 baseball program when coming from D3 program? It seems challenging.